Register allocation problems with TLS unit test.

Running the SingleSource tests with llc while debugging my PBQP
allocator I noticed that
test-suite/SingleSource/UnitTests/Threads/tls.c has some issues with
register allocators other than linear scan:

Local, simple & bigblock regalloc all cause the following ld assertion failures:

bash-3.2$ gcc tls.foo.s -o tls.foo.debug -lm -lpthread
/usr/bin/ld: BFD version 2.17.50.0.18-1 20070731 assertion fail
../../bfd/elf64-x86-64.c:2561
/usr/bin/ld: BFD version 2.17.50.0.18-1 20070731 assertion fail
../../bfd/elf64-x86-64.c:2566
/usr/bin/ld: BFD version 2.17.50.0.18-1 20070731 assertion fail
../../bfd/elf64-x86-64.c:2568

The resulting code segfaults on execution. I haven't figured out
exactly why yet. Will post more details when I figure them out.

If it helps my system is an AMD64 running Ubuntu and LLVM SVN.

Cheers,
Lang.