cmd/go: update alldocs.go

Also added go:generate directive.

Change-Id: Ib1f0eddc75e3c47a4d904786a29b964a35b18456
Reviewed-on: https://go-review.googlesource.com/21042Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>

src/cmd/go/doc.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:generate ./mkalldocs.sh
+
 package main
 
 var cmdDoc = &Command{

src/cmd/go/mkalldocs.sh

 #!/bin/bash
-# Copyright 2012 The Go Authors.  All rights reserved.
+# 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.