libgo: Update to go1.6rc1.

Reviewed-on: https://go-review.googlesource.com/19200

From-SVN: r233110

libgo/go/runtime/testdata/testprog/misc.go

@@ -0,0 +1,15 @@
+// Copyright 2016 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "runtime"
+
+func init() {
+	register("NumGoroutine", NumGoroutine)
+}
+
+func NumGoroutine() {
+	println(runtime.NumGoroutine())
+}