syscall: use error

- syscall (not os) now defines the Errno type.
- the low-level assembly functions Syscall, Syscall6, and so on
  return Errno, not uintptr
- syscall wrappers all return error, not uintptr.

R=golang-dev, mikioh.mikioh, r, alex.brainman
CC=golang-dev
https://golang.org/cl/5372080
diff --git a/src/pkg/syscall/zerrors_openbsd_amd64.go b/src/pkg/syscall/zerrors_openbsd_amd64.go
index e625741..c6367fb 100644
--- a/src/pkg/syscall/zerrors_openbsd_amd64.go
+++ b/src/pkg/syscall/zerrors_openbsd_amd64.go
@@ -149,108 +149,13 @@
 	DT_REG                            = 0x8
 	DT_SOCK                           = 0xc
 	DT_UNKNOWN                        = 0x0
-	E2BIG                             = 0x7
-	EACCES                            = 0xd
-	EADDRINUSE                        = 0x30
-	EADDRNOTAVAIL                     = 0x31
-	EAFNOSUPPORT                      = 0x2f
-	EAGAIN                            = 0x23
-	EALREADY                          = 0x25
-	EAUTH                             = 0x50
-	EBADF                             = 0x9
-	EBADRPC                           = 0x48
-	EBUSY                             = 0x10
-	ECANCELED                         = 0x58
-	ECHILD                            = 0xa
-	ECHO                              = 0x8
-	ECHOCTL                           = 0x40
-	ECHOE                             = 0x2
-	ECHOK                             = 0x4
-	ECHOKE                            = 0x1
-	ECHONL                            = 0x10
-	ECHOPRT                           = 0x20
-	ECONNABORTED                      = 0x35
-	ECONNREFUSED                      = 0x3d
-	ECONNRESET                        = 0x36
-	EDEADLK                           = 0xb
-	EDESTADDRREQ                      = 0x27
-	EDOM                              = 0x21
-	EDQUOT                            = 0x45
-	EEXIST                            = 0x11
-	EFAULT                            = 0xe
-	EFBIG                             = 0x1b
 	EFER_LMA                          = 0x400
 	EFER_LME                          = 0x100
 	EFER_NXE                          = 0x800
 	EFER_SCE                          = 0x1
-	EFTYPE                            = 0x4f
-	EHOSTDOWN                         = 0x40
-	EHOSTUNREACH                      = 0x41
-	EIDRM                             = 0x59
-	EILSEQ                            = 0x54
-	EINPROGRESS                       = 0x24
-	EINTR                             = 0x4
-	EINVAL                            = 0x16
-	EIO                               = 0x5
-	EIPSEC                            = 0x52
-	EISCONN                           = 0x38
-	EISDIR                            = 0x15
-	ELAST                             = 0x5b
-	ELOOP                             = 0x3e
-	EMEDIUMTYPE                       = 0x56
-	EMFILE                            = 0x18
-	EMLINK                            = 0x1f
-	EMSGSIZE                          = 0x28
 	EMT_TAGOVF                        = 0x1
 	EMUL_ENABLED                      = 0x1
 	EMUL_NATIVE                       = 0x2
-	ENAMETOOLONG                      = 0x3f
-	ENDRUNDISC                        = 0x9
-	ENEEDAUTH                         = 0x51
-	ENETDOWN                          = 0x32
-	ENETRESET                         = 0x34
-	ENETUNREACH                       = 0x33
-	ENFILE                            = 0x17
-	ENOATTR                           = 0x53
-	ENOBUFS                           = 0x37
-	ENODEV                            = 0x13
-	ENOENT                            = 0x2
-	ENOEXEC                           = 0x8
-	ENOLCK                            = 0x4d
-	ENOMEDIUM                         = 0x55
-	ENOMEM                            = 0xc
-	ENOMSG                            = 0x5a
-	ENOPROTOOPT                       = 0x2a
-	ENOSPC                            = 0x1c
-	ENOSYS                            = 0x4e
-	ENOTBLK                           = 0xf
-	ENOTCONN                          = 0x39
-	ENOTDIR                           = 0x14
-	ENOTEMPTY                         = 0x42
-	ENOTSOCK                          = 0x26
-	ENOTSUP                           = 0x5b
-	ENOTTY                            = 0x19
-	ENXIO                             = 0x6
-	EOPNOTSUPP                        = 0x2d
-	EOVERFLOW                         = 0x57
-	EPERM                             = 0x1
-	EPFNOSUPPORT                      = 0x2e
-	EPIPE                             = 0x20
-	EPROCLIM                          = 0x43
-	EPROCUNAVAIL                      = 0x4c
-	EPROGMISMATCH                     = 0x4b
-	EPROGUNAVAIL                      = 0x4a
-	EPROTONOSUPPORT                   = 0x2b
-	EPROTOTYPE                        = 0x29
-	ERANGE                            = 0x22
-	EREMOTE                           = 0x47
-	EROFS                             = 0x1e
-	ERPCMISMATCH                      = 0x49
-	ESHUTDOWN                         = 0x3a
-	ESOCKTNOSUPPORT                   = 0x2c
-	ESPIPE                            = 0x1d
-	ESRCH                             = 0x3
-	ESTALE                            = 0x46
 	ETHERMIN                          = 0x2e
 	ETHERMTU                          = 0x5dc
 	ETHERTYPE_8023                    = 0x4
@@ -449,10 +354,6 @@
 	ETHER_MIN_LEN                     = 0x40
 	ETHER_TYPE_LEN                    = 0x2
 	ETHER_VLAN_ENCAP_LEN              = 0x4
-	ETIMEDOUT                         = 0x3c
-	ETOOMANYREFS                      = 0x3b
-	ETXTBSY                           = 0x1a
-	EUSERS                            = 0x44
 	EVFILT_AIO                        = -0x3
 	EVFILT_PROC                       = -0x5
 	EVFILT_READ                       = -0x1
@@ -471,8 +372,6 @@
 	EV_FLAG1                          = 0x2000
 	EV_ONESHOT                        = 0x10
 	EV_SYSFLAGS                       = 0xf000
-	EWOULDBLOCK                       = 0x23
-	EXDEV                             = 0x12
 	EXTA                              = 0x4b00
 	EXTB                              = 0x9600
 	EXTPROC                           = 0x800
@@ -1268,6 +1167,111 @@
 	WUNTRACED                         = 0x2
 )
 
+// Errors
+const (
+	E2BIG           = Errno(0x7)
+	EACCES          = Errno(0xd)
+	EADDRINUSE      = Errno(0x30)
+	EADDRNOTAVAIL   = Errno(0x31)
+	EAFNOSUPPORT    = Errno(0x2f)
+	EAGAIN          = Errno(0x23)
+	EALREADY        = Errno(0x25)
+	EAUTH           = Errno(0x50)
+	EBADF           = Errno(0x9)
+	EBADRPC         = Errno(0x48)
+	EBUSY           = Errno(0x10)
+	ECANCELED       = Errno(0x58)
+	ECHILD          = Errno(0xa)
+	ECHO            = Errno(0x8)
+	ECHOCTL         = Errno(0x40)
+	ECHOE           = Errno(0x2)
+	ECHOK           = Errno(0x4)
+	ECHOKE          = Errno(0x1)
+	ECHONL          = Errno(0x10)
+	ECHOPRT         = Errno(0x20)
+	ECONNABORTED    = Errno(0x35)
+	ECONNREFUSED    = Errno(0x3d)
+	ECONNRESET      = Errno(0x36)
+	EDEADLK         = Errno(0xb)
+	EDESTADDRREQ    = Errno(0x27)
+	EDOM            = Errno(0x21)
+	EDQUOT          = Errno(0x45)
+	EEXIST          = Errno(0x11)
+	EFAULT          = Errno(0xe)
+	EFBIG           = Errno(0x1b)
+	EFTYPE          = Errno(0x4f)
+	EHOSTDOWN       = Errno(0x40)
+	EHOSTUNREACH    = Errno(0x41)
+	EIDRM           = Errno(0x59)
+	EILSEQ          = Errno(0x54)
+	EINPROGRESS     = Errno(0x24)
+	EINTR           = Errno(0x4)
+	EINVAL          = Errno(0x16)
+	EIO             = Errno(0x5)
+	EIPSEC          = Errno(0x52)
+	EISCONN         = Errno(0x38)
+	EISDIR          = Errno(0x15)
+	ELAST           = Errno(0x5b)
+	ELOOP           = Errno(0x3e)
+	EMEDIUMTYPE     = Errno(0x56)
+	EMFILE          = Errno(0x18)
+	EMLINK          = Errno(0x1f)
+	EMSGSIZE        = Errno(0x28)
+	ENAMETOOLONG    = Errno(0x3f)
+	ENDRUNDISC      = Errno(0x9)
+	ENEEDAUTH       = Errno(0x51)
+	ENETDOWN        = Errno(0x32)
+	ENETRESET       = Errno(0x34)
+	ENETUNREACH     = Errno(0x33)
+	ENFILE          = Errno(0x17)
+	ENOATTR         = Errno(0x53)
+	ENOBUFS         = Errno(0x37)
+	ENODEV          = Errno(0x13)
+	ENOENT          = Errno(0x2)
+	ENOEXEC         = Errno(0x8)
+	ENOLCK          = Errno(0x4d)
+	ENOMEDIUM       = Errno(0x55)
+	ENOMEM          = Errno(0xc)
+	ENOMSG          = Errno(0x5a)
+	ENOPROTOOPT     = Errno(0x2a)
+	ENOSPC          = Errno(0x1c)
+	ENOSYS          = Errno(0x4e)
+	ENOTBLK         = Errno(0xf)
+	ENOTCONN        = Errno(0x39)
+	ENOTDIR         = Errno(0x14)
+	ENOTEMPTY       = Errno(0x42)
+	ENOTSOCK        = Errno(0x26)
+	ENOTSUP         = Errno(0x5b)
+	ENOTTY          = Errno(0x19)
+	ENXIO           = Errno(0x6)
+	EOPNOTSUPP      = Errno(0x2d)
+	EOVERFLOW       = Errno(0x57)
+	EPERM           = Errno(0x1)
+	EPFNOSUPPORT    = Errno(0x2e)
+	EPIPE           = Errno(0x20)
+	EPROCLIM        = Errno(0x43)
+	EPROCUNAVAIL    = Errno(0x4c)
+	EPROGMISMATCH   = Errno(0x4b)
+	EPROGUNAVAIL    = Errno(0x4a)
+	EPROTONOSUPPORT = Errno(0x2b)
+	EPROTOTYPE      = Errno(0x29)
+	ERANGE          = Errno(0x22)
+	EREMOTE         = Errno(0x47)
+	EROFS           = Errno(0x1e)
+	ERPCMISMATCH    = Errno(0x49)
+	ESHUTDOWN       = Errno(0x3a)
+	ESOCKTNOSUPPORT = Errno(0x2c)
+	ESPIPE          = Errno(0x1d)
+	ESRCH           = Errno(0x3)
+	ESTALE          = Errno(0x46)
+	ETIMEDOUT       = Errno(0x3c)
+	ETOOMANYREFS    = Errno(0x3b)
+	ETXTBSY         = Errno(0x1a)
+	EUSERS          = Errno(0x44)
+	EWOULDBLOCK     = Errno(0x23)
+	EXDEV           = Errno(0x12)
+)
+
 // Error table
 var errors = [...]string{
 	1:  "operation not permitted",