build: move package sources from src/pkg to src

Preparation was in CL 134570043.
This CL contains only the effect of 'hg mv src/pkg/* src'.
For more about the move, see golang.org/s/go14nopkg.

src/pkg/runtime/signal_unix.go

@@ -1,13 +0,0 @@
-// Copyright 2012 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.
-
-// +build darwin dragonfly freebsd linux netbsd openbsd solaris
-
-package runtime
-
-func sigpipe()
-
-func os_sigpipe() {
-	onM(sigpipe)
-}