SkJumper: tiling modes

Slight changes to clamp to make it look more like the other two.

Mirror gets a fun new SSE/AVX abs() that requires no constants:

    abs(v) = v & (0-v)

Change-Id: Iab4a61e39a7d28b47d9a10e7283df58b5e5a034e
Reviewed-on: https://skia-review.googlesource.com/8950
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
4 files changed