fix incorrect assumption in gdb.ada/watch_arg

The testcase is assuming that the parameter being watched isn't being
modified. But the way the test program is written, this is not true
at all.  So this changes fixes the code to still reference the variable,
but in a way that does not modify its value.

gdb/testsuite:

        * gdb.ada/watch_arg/pck.ads, gdb.ada/watch_arg/pck.adb: New files.
        * gdb.ada/watch_arg/watch.adb: Adjust code to avoid modification
        of parameter X in procedure Foo.

gdb/testsuite/ChangeLog

@@ -1,3 +1,9 @@
+2011-12-06  Joel Brobecker  <brobecker@adacore.com>
+
+	* gdb.ada/watch_arg/pck.ads, gdb.ada/watch_arg/pck.adb: New files.
+	* gdb.ada/watch_arg/watch.adb: Adjust code to avoid modification
+	of parameter X in procedure Foo.
+
 2011-12-05  Stan Shebs  <stan@codesourcery.com>
 
 	* gdb.trace/tfind.exp: Update help string matches.

gdb/testsuite/gdb.ada/watch_arg/pck.adb

@@ -0,0 +1,23 @@
+--  Copyright 2011 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/>.
+
+package body Pck is
+
+   procedure Do_Nothing (A : System.Address) is
+   begin
+      null;
+   end Do_Nothing;
+
+end Pck;

gdb/testsuite/gdb.ada/watch_arg/pck.ads

@@ -0,0 +1,19 @@
+--  Copyright 2011 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/>.
+
+with System;
+package Pck is
+   procedure Do_Nothing (A : System.Address);
+end Pck;

gdb/testsuite/gdb.ada/watch_arg/watch.adb

@@ -14,11 +14,14 @@
 --  You should have received a copy of the GNU General Public License
 --  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+with Pck; use Pck;
+
 procedure Watch is
 
    procedure Foo (X : in out Integer) is
    begin
-      X := 3;  -- BREAK1
+      --  Reference X in a way that does not change its value.
+      Do_Nothing (X'Address);  -- BREAK1
    end Foo;
 
    X : Integer := 1;