RFC: Add AIX .ref support

[Richard Sandiford]

Nick Clifton <nickc@redhat.com> writes:
> Hi Richard,
>
>> Tested on powerpc-ibm-aix6.1.
>
> Please run a regression test with an x86 or x86_64 toolchain, just to be 
> sure.

Thanks, committed after testing on x86_64-linux-gnu.

Tristan, you said on gcc-patches@ that we could put the .ref support
in binutils 2.20.1.  Are you still OK with that?  Is it OK to apply
the patch to the branch?

Richard