gas testsuite fixes for arm-vxworks

[Nick Clifton]

Hi Zack,

>>gas/testsuite
>>        * lib/gas-defs.exp (run_dump_tests): New proc.
>>        (run_dump_test): Add support for new options: target, not-target,
>>        skip, not-skip, error-output.  Document stderr.  Tidy a
>>        little.
>>        (slurp_options): If a line doesn't match the option regexp, but
>>        does begin with #, ignore it; don't stop parsing options.

> The ARM bits look fine, but you'll need someone like Nick to approve the
> generic bits.

The generic part is OK too, so please go ahead and apply this patch.

Cheers
   Nick