Enable sse2 backend for SkSplicer.

Enable sse2 backend for SkSplicer.

One more piece of https://skia-review.googlesource.com/c/8230/.

-mno-red-zone makes it safe for x86 stages to use the stack on Windows
(at the expense of an extra sub and add to the stack pointer on !Windows).

CQ_INCLUDE_TRYBOTS=skia.primary:Test-Win2k8-MSVC-GCE-CPU-AVX2-x86_64-Debug,Test-Win10-MSVC-Golo-GPU-GT610-x86_64-Release,Test-Mac-Clang-MacMini6.2-CPU-AVX-x86_64-Debug

Change-Id: I81f8220e790b201757a7e1e9752b2fe94520ccbb
Reviewed-on: https://skia-review.googlesource.com/8352
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Herb Derby <herb@google.com>