-march=core2 implies support for both the SSE3 and SSSE3 instruction
set extensions. Chrome should run on CPUs with only SSE2 as well.

Also, make use of SSE on x86-32 for floating-point operations, to be
consistent with x86-64, and don't favor any specific architecture for
tuning.

Bug chromium:797763

Change-Id: Ia17428734460ed855f3aa0f83c6d2f6b3775094c
Reviewed-on: https://swiftshader-review.googlesource.com/15688Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>