powerpc-vxworks testers needed

[Jerome Guitton]

Alan Modra (amodra@gmail.com):

> Now, I don't have access to a powerpc-vxworks system, so this patch
> might leave vxworks broken due to additional features being enabled.
> For example, TLS optimisation will now occur on powerpc-vxworks, and
> I don't have any information on how TLS is implemented on vxworks.
> Hopefully, it follows my original ppc tls implementation in terms of
> code and reloc sequences..  If not, I'd like to hear about problems
> now rather than a week or so after the next binutils release.  ;)

FWIW, I've tested this patch against our internal Ada testsuites in
rtp/smp (the only configuration where we know that TLS would have an
impact). No regression.