Running gas testsuite

[Stephen Casner]

p.s. In my opinion, it would be a benefit to change the gas/Makefile
so that when I go looking for the gas.log I find it in the gas
directory just like for ld.log in the ld directory and binutils.log in
the binutils subdirectory rather than finding it in gas/testsuite.

I recognize that changing this might have an impact on Nick's (and
perhaps others') infrastructure for testing all the different targets.
So we should hear from any dissenting opinions.

                                                        -- Steve