Revert of SkPx: new approach to fixed-point SIMD (patchset #12 id:220001 of https...

Revert of SkPx: new approach to fixed-point SIMD (patchset #12 id:220001 of https://codereview.chromium.org/1317233005/ )

Reason for revert:
master-skia unhappy:
https://android-build.storage.googleapis.com/builds/git_master-skia-linux-volantis-userdebug/2404853/e6c439e806fb0bd0f872a3d7a5cf0637d4ad11bfaa89e9bc18b651dc65f0a36b/logs/build_error.log?GoogleAccessId=701025073339-mqn0q2nvir9iurm6q5d00tdv7blbgvjr%40developer.gserviceaccount.com&Signature=WOqQO7xHkv83SmC4h5tNUIp%2BREaYULqK11hNTWlhj1XXo0NAOQd7GNSIHl775uRRZpBw2LkHeb2Ups3LsgRPrldqymposFtDa%2BUEW0Jv2NWAr%2F1Cqt6lwWsfknvJLN9NiEGfpCCye3Q%2FEYx9bU1ozMBG6h2DRHJUMRS%2FjstkJg0%3D&Expires=1446838937

Original issue's description:
> SkPx: new approach to fixed-point SIMD
>
> SkPx is like Sk4px, except each platform implementation of SkPx can declare
> a different sweet spot of N pixels, with extra loads and stores to handle the
> ragged edge of 0<n<N pixels.
>
> In this case, _sse's sweet spot remains 4 pixels.   _neon jumps up to 8 so
> we can now use NEON's transposing loads and stores, and _none is just 1.
> This makes operations involving alpha considerably more efficient on NEON,
> as alpha is its own distinct 8x8 bit plane that's easy to toss around.
>
> This incorporates a few other improvements I've been wanting:
>   - no requirement that we're dealing with SkPMColor.  SkColor works too.
>   - no anonymous namespace hack to differentiate implementations.
>
> Codegen and perf look good on Clang/x86-64 and GCC/ARMv7.
> The NEON code looks very similar to the old NEON code, as intended.
> No .skp or GM diffs on my laptop.  Don't expect any.
>
> I intend this to replace Sk4px.  Plan after landing:
>   - port SkXfermode_opts.h
>   - port Color32 in SkBlitRow_D32.cpp (and move to SkBlitRow_opts.h like other
>     SkOpts code)
>   - delete all Sk4px-related code
>   - clean up evolutionary dead ends in SkNx (Sk16b, Sk16h, Sk4i, Sk4d, etc.)
>     leaving Sk2f, Sk4f (and Sk2s, Sk4s).
>   - find a machine with AVX2 to work on, write SkPx_avx2.h handling 8 pixels
>     at a time.
>
> In the end we'll have Sk4f for float pixels, SkPx for fixed-point pixels.
>
> BUG=skia:4117
>
> Committed: https://skia.googlesource.com/skia/+/82c93b45ed6ac0b628adb8375389c202d1f586f9
>
> CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot;client.skia.compile:Build-Mac10.8-Clang-Arm7-Debug-Android-Trybot
>
> Committed: https://skia.googlesource.com/skia/+/a7627dc5cc2bf5d9a95d883d20c40d477ecadadf

TBR=msarett@google.com,mtklein@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:4117

Review URL: https://codereview.chromium.org/1409843005