lib/gdb.exp: New gdb_test_no_output function.

lib/gdb.exp: New gdb_test_no_output function.

This new testsuite routine allows us to test commands that are not
expected to generate any output.

2010-05-20  Pedro Alves  <pedro@codesourcery.com>
            Joel Brobecker  <brobecker@adacore.com>

        * lib/gdb.exp (gdb_test_no_output): New function.
        * lib/gdb.ada/arrayidx.exp: Use gdb_test_no_output instead of gdb_test
        when testing commands that should produce no output.

Tested on x86_64-linux.