[patch] Drop support for non-cfi capable assemblers

[Rafael Espíndola]

> I do for SPARC, that makes up 2 out of the 3 OS's that are being used and
> targetted so far.
>
> What prevents FreeBSD / OpenBSD from upgrading is the license.

This is incorrect.  The license change was done in
ec2655a6a75bc61d21e6f8ddc1e9f9027a8914dd in 2007. Gas already had
support for cfi before that. I tested building the previous revision
with --target=sparc64-pc-freebsd and it was more than happy to
assembly llc's output of test/CodeGen/SPARC/exception.ll,
.cfi_window_save and all.

Cheers,
Rafael