syscall: on freebsd, darwin, give Kill same signature as on linux

R=r, cw
CC=golang-dev
https://golang.org/cl/201043
diff --git a/src/pkg/syscall/syscall_darwin.go b/src/pkg/syscall/syscall_darwin.go
index 20f9fa2..1946ecd 100644
--- a/src/pkg/syscall/syscall_darwin.go
+++ b/src/pkg/syscall/syscall_darwin.go
@@ -454,6 +454,10 @@
 	return *(*uint32)(unsafe.Pointer(&buf[0])), 0
 }
 
+//sys	kill(pid int, signum int, posix int) (errno int)
+
+func Kill(pid int, signum int) (errno int) { return kill(pid, signum, 1) }
+
 // TODO: wrap
 //	Acct(name nil-string) (errno int)
 //	Futimes(fd int, timeval *Timeval) (errno int)	// Pointer to 2 timevals!
@@ -511,7 +515,6 @@
 //sys	Getsid(pid int) (sid int, errno int)
 //sys	Getuid() (uid int)
 //sys	Issetugid() (tainted bool)
-//sys	Kill(pid int, signum int, posix int) (errno int)
 //sys	Kqueue() (fd int, errno int)
 //sys	Lchown(path string, uid int, gid int) (errno int)
 //sys	Link(path string, link string) (errno int)