testshared/src/depBase: conform build tag comment to convention

Also add missing copyright headers with year determined from git log.

Change-Id: Iafc9881e746543f0a582dad2b0874d8399baf618
Reviewed-on: https://go-review.googlesource.com/122415Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

misc/cgo/testshared/src/depBase/asm.s

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !gccgo
+// +build !gccgo
 
 #include "textflag.h"
 

misc/cgo/testshared/src/depBase/dep.go

+// 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 depBase
 
 import (

misc/cgo/testshared/src/depBase/gccgo.go

-//+build gccgo
+// 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.
+
+// +build gccgo
 
 package depBase
 

misc/cgo/testshared/src/depBase/stubs.go

-//+build !gccgo
+// 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.
+
+// +build !gccgo
 
 package depBase