syscall: add Flock on Linux

Fixes #2069.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/4703048

src/pkg/syscall/syscall_linux.go

diff --git a/src/pkg/syscall/syscall_linux.go b/src/pkg/syscall/syscall_linux.go
index 1d6fc76..9fc2605 100644
--- a/src/pkg/syscall/syscall_linux.go
+++ b/src/pkg/syscall/syscall_linux.go
@@ -774,6 +774,7 @@
 //sys	Fchownat(dirfd int, path string, uid int, gid int, flags int) (errno int)
 //sys	fcntl(fd int, cmd int, arg int) (val int, errno int)
 //sys	Fdatasync(fd int) (errno int)
+//sys	Flock(fd int, how int) (errno int)
 //sys	Fsync(fd int) (errno int)
 //sys	Getdents(fd int, buf []byte) (n int, errno int) = SYS_GETDENTS64
 //sysnb	Getpgid(pid int) (pgid int, errno int)
@@ -878,7 +879,6 @@
 // Fadvise64
 // Fgetxattr
 // Flistxattr
-// Flock
 // Fork
 // Fremovexattr
 // Fsetxattr

src/pkg/syscall/zsyscall_linux_386.go

diff --git a/src/pkg/syscall/zsyscall_linux_386.go b/src/pkg/syscall/zsyscall_linux_386.go
index 8df29f13..4eb522a 100644
--- a/src/pkg/syscall/zsyscall_linux_386.go
+++ b/src/pkg/syscall/zsyscall_linux_386.go
@@ -277,6 +277,14 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Flock(fd int, how int) (errno int) {
+	_, _, e1 := Syscall(SYS_FLOCK, uintptr(fd), uintptr(how), 0)
+	errno = int(e1)
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Fsync(fd int) (errno int) {
 	_, _, e1 := Syscall(SYS_FSYNC, uintptr(fd), 0, 0)
 	errno = int(e1)

src/pkg/syscall/zsyscall_linux_amd64.go

diff --git a/src/pkg/syscall/zsyscall_linux_amd64.go b/src/pkg/syscall/zsyscall_linux_amd64.go
index fa20ff5..999ed64 100644
--- a/src/pkg/syscall/zsyscall_linux_amd64.go
+++ b/src/pkg/syscall/zsyscall_linux_amd64.go
@@ -277,6 +277,14 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Flock(fd int, how int) (errno int) {
+	_, _, e1 := Syscall(SYS_FLOCK, uintptr(fd), uintptr(how), 0)
+	errno = int(e1)
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Fsync(fd int) (errno int) {
 	_, _, e1 := Syscall(SYS_FSYNC, uintptr(fd), 0, 0)
 	errno = int(e1)

src/pkg/syscall/zsyscall_linux_arm.go

diff --git a/src/pkg/syscall/zsyscall_linux_arm.go b/src/pkg/syscall/zsyscall_linux_arm.go
index 560a65b..cd49dab 100644
--- a/src/pkg/syscall/zsyscall_linux_arm.go
+++ b/src/pkg/syscall/zsyscall_linux_arm.go
@@ -277,6 +277,14 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Flock(fd int, how int) (errno int) {
+	_, _, e1 := Syscall(SYS_FLOCK, uintptr(fd), uintptr(how), 0)
+	errno = int(e1)
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Fsync(fd int) (errno int) {
 	_, _, e1 := Syscall(SYS_FSYNC, uintptr(fd), 0, 0)
 	errno = int(e1)