syscall: move bsd pipe syscall

Not all BSDs have the same pipe() syscall implementation - move the Darwin/FreeBSD specific implementation into their respective OS syscall files. This will be needed to add OpenBSD syscall support.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4823057

src/pkg/syscall/syscall_bsd.go

@@ -135,16 +135,6 @@ func Wait4(pid int, wstatus *WaitStatus, options int, rusage *Rusage) (wpid int,
 	return
 }
 
-//sysnb	pipe() (r int, w int, errno int)
-
-func Pipe(p []int) (errno int) {
-	if len(p) != 2 {
-		return EINVAL
-	}
-	p[0], p[1], errno = pipe()
-	return
-}
-
 func Sleep(ns int64) (errno int) {
 	tv := NsecToTimeval(ns)
 	return Select(0, nil, nil, nil, &tv)

src/pkg/syscall/syscall_darwin.go

@@ -60,6 +60,16 @@ func ParseDirent(buf []byte, max int, names []string) (consumed int, count int,
 func PtraceAttach(pid int) (errno int) { return ptrace(PT_ATTACH, pid, 0, 0) }
 func PtraceDetach(pid int) (errno int) { return ptrace(PT_DETACH, pid, 0, 0) }
 
+//sysnb pipe() (r int, w int, errno int)
+
+func Pipe(p []int) (errno int) {
+	if len(p) != 2 {
+		return EINVAL
+	}
+	p[0], p[1], errno = pipe()
+	return
+}
+
 // TODO
 func Sendfile(outfd int, infd int, offset *int64, count int) (written int, errno int) {
 	return -1, ENOSYS

src/pkg/syscall/syscall_freebsd.go

@@ -56,6 +56,16 @@ func ParseDirent(buf []byte, max int, names []string) (consumed int, count int,
 	return origlen - len(buf), count, names
 }
 
+//sysnb pipe() (r int, w int, errno int)
+
+func Pipe(p []int) (errno int) {
+	if len(p) != 2 {
+		return EINVAL
+	}
+	p[0], p[1], errno = pipe()
+	return
+}
+
 // TODO
 func Sendfile(outfd int, infd int, offset *int64, count int) (written int, errno int) {
 	return -1, ENOSYS