gallivm: Translate all util_cpu_caps bits to LLVM attributes.

gallivm: Translate all util_cpu_caps bits to LLVM attributes.

This should prevent disparity between features Mesa and LLVM
believe are supported by the CPU.

http://lists.freedesktop.org/archives/mesa-dev/2015-October/thread.html#96990

Tested on a i7-3720QM w/ LLVM 3.3 and 3.6.

v2: Increase SmallVector initial size as suggested by Gustaw Smolarczyk.

Reviewed-by: Roland Scheidegger <sroland@vmware.com>
CC: "10.6 11.0" <mesa-stable@lists.freedesktop.org>
(cherry picked from commit 718249843b915decf8fccec92e466ac1a6219934)