make parameter being watched is a non-constant.

make parameter being watched is a non-constant.

The gdb.ada/watch_arg testcase is testing a situation where we are
leaving the scope where a parameter being watched is defined. The
testcase is a little non-sensical that we're watching a parameter
declared as an "access integer", which in non-Ada terms means
a constant pointer.  Doesn't make much sense to watch a constant...

So this patch changes the code a little to use an "in out Integer",
which makes the parameter a non-constant integer, rather than a
constant access Integer.  I verified that I could still reproduce
the problem with the original debugger and the modified testcase.

This was motivated by a patch that Sergio is about to submit which
will forbid the user from watching a constant (discussed on IRC)

2010-05-17  Joel Brobecker  <brobecker@adacore.com>

        * gdb.ada/watch_arg/watch.adb: Rewrite testcase to avoid the
        parameter that we want to watch being a constant.

Tested on both sparc-solaris (where the ancient debugger could still
run ;-), and on x86_64-linux.