syscalls/sleep_rtems.go: Add missing package clause.

From-SVN: r169183

libgo/syscalls/sleep_rtems.go

@@ -4,6 +4,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+package syscall
+
 func libc_nanosleep(req *Timespec, rem *Timespec) int __asm__ ("nanosleep")
 
 func Sleep(nsec int64) (errno int) {