Have Windows use _mm_rsqrt_ss too.

Have Windows use _mm_rsqrt_ss too.

Tidy up a little while I'm in here:
  1) SIMD headers are now included by SkTypes.h as appropriate.
  2) _mm_cvtss_f32() is pithier and generates the same code.

Looks like this is the only code checking for SSE wrong.  After this CL:
    ~/skia (sse) $ git grep __SSE
    include/core/SkPreConfig.h:    #if defined(__SSE4_2__)
    include/core/SkPreConfig.h:    #elif defined(__SSE4_1__)
    include/core/SkPreConfig.h:    #elif defined(__SSE3__)
    include/core/SkPreConfig.h:    #elif defined(__SSE2__)
every other check is in SkPreConfig.h where it belongs.

This is going to affect some GMs subtly on Windows.

BUG=chromium:511458
No public API changes.
TBR=reed@google.com

Committed: https://skia.googlesource.com/skia/+/b9c47f996867ec885a7ede697bd1b0859b6d9301

[mtklein_C, 2015-07-23 15:24:52]

mtklein@chromium.org changed reviewers:
+ jvanverth@google.com

[mtklein_C, 2015-07-23 15:29:02]

The CQ bit was checked by mtklein@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-07-23 15:29:08]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1248503004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1248503004/1

[jvanverth1, 2015-07-23 15:31:59]

LGTM

[mtklein, 2015-07-23 15:33:55]

The CQ bit was unchecked by mtklein@google.com

[mtklein, 2015-07-23 15:34:01]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2015-07-23 15:34:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1248503004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1248503004/1

[commit-bot: I haz the power, 2015-07-23 15:37:05]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/b9c47f996867ec885a7ede697bd1b0859b6d9301