Implement saturated vector add/subtract.

BUG=swiftshader:15

Change-Id: Ic120eddd1761e33b7d76bf3ed8ec5ca74634f958
Reviewed-on: https://chromium-review.googlesource.com/403477
Reviewed-by: Jim Stichnoth <stichnot@chromium.org>
Tested-by: Nicolas Capens <nicolascapens@google.com>
6 files changed