os/syscall: correct netbsd types/names

Fix types/names so that these functions work with the generated
syscall/z* files.

R=golang-dev, m4dh4tt3r
CC=golang-dev
https://golang.org/cl/6201078
diff --git a/src/pkg/syscall/syscall_netbsd_386.go b/src/pkg/syscall/syscall_netbsd_386.go
index 3c4c693..2dbff07 100644
--- a/src/pkg/syscall/syscall_netbsd_386.go
+++ b/src/pkg/syscall/syscall_netbsd_386.go
@@ -9,7 +9,7 @@
 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }
 
 func NsecToTimespec(nsec int64) (ts Timespec) {
-	ts.Sec = int32(nsec / 1e9)
+	ts.Sec = int64(nsec / 1e9)
 	ts.Nsec = int32(nsec % 1e9)
 	return
 }
@@ -19,14 +19,14 @@
 func NsecToTimeval(nsec int64) (tv Timeval) {
 	nsec += 999 // round up to microsecond
 	tv.Usec = int32(nsec % 1e9 / 1e3)
-	tv.Sec = int32(nsec / 1e9)
+	tv.Sec = int64(nsec / 1e9)
 	return
 }
 
 func SetKevent(k *Kevent_t, fd, mode, flags int) {
 	k.Ident = uint32(fd)
-	k.Filter = int16(mode)
-	k.Flags = uint16(flags)
+	k.Filter = uint32(mode)
+	k.Flags = uint32(flags)
 }
 
 func (iov *Iovec) SetLen(length int) {