All //sys instructions moved to separate syscall_* files

Generated `syscall_*` files ranamed to `zsyscall_*` ones
like it done in `golang.org/x/sys` package.

syscall_freebsd.go

@@ -4,18 +4,6 @@
 // license that can be found in the LICENSE file.
 //
 
-// This file is machine generated by the command:
-//   mksyscall.pl serial_darwin.go
-// The generated stub is modified to make it compile under the "serial" package
-
 package serial // import "go.bug.st/serial.v1"
 
-import "syscall"
-
-func ioctl(fd int, req uint64, data uintptr) (err error) {
-	_, _, e1 := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), uintptr(req), uintptr(data))
-	if e1 != 0 {
-		err = e1
-	}
-	return
-}
+//sys ioctl(fd int, req uint64, data uintptr) (err error)