Add copyright header in gdb.base/return.c

gdb/testsuite:

2016-06-29  Yao Qi  <yao.qi@linaro.org>

	* gdb.base/return.c: Add copyright header.

gdb/testsuite/ChangeLog

+2016-06-29  Yao Qi  <yao.qi@linaro.org>
+
+	* gdb.base/return.c: Add copyright header.
+
 2016-06-29  Tom Tromey  <tom@tromey.com>
 
 	PR python/20129:

gdb/testsuite/gdb.base/return.c

+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 1992-2016 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
 #include <stdio.h>
 /*  Test "return" command.  */