Specialize Sk2d for ARM64

Specialize Sk2d for ARM64

The implementation is nearly identical to Sk2f, with these changes:
  - float32x2_t -> float64x2_t
  - vfoo -> vfooq
  - one extra Newton's method step in sqrt().

Also, generally fix NEON detection to be defined(SK_ARM_HAS_NEON).
SK_ARM_HAS_NEON is not being set on ARM64 bots right now (nor does the compiler
seem to set __ARM_NEON__), so this CL fixes everything up.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/e57b5cab261a243dcbefa74c91c896c28959bf09

CQ_EXTRA_TRYBOTS=client.skia.compile:Build-Mac10.7-Clang-Arm7-Debug-iOS-Trybot,Build-Ubuntu-GCC-Arm64-Release-Android-Trybot

Committed: https://skia.googlesource.com/skia/+/b79ff56de23fef680ae7187040f2d6a9516b553d

[mtklein_C, 2015-03-19 20:51:56]

mtklein@chromium.org changed reviewers:
+ msarett@google.com, reed@google.com

[reed1, 2015-03-19 21:13:48]

api lgtm

[mtklein, 2015-03-20 14:58:25]

mtklein@google.com changed reviewers:
+ mtklein@google.com

[mtklein, 2015-03-20 14:58:26]

Going to land this now so I can start building more on it.

[mtklein, 2015-03-20 14:58:30]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2015-03-20 14:58:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1020963002/20001

[commit-bot: I haz the power, 2015-03-20 14:58:45]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-03-20 14:58:46]

Failed to apply patch for src/core/Sk2x.h:
While running git apply --index -3 -p1;
  error: patch failed: src/core/Sk2x.h:13
  Falling back to three-way merge...
  Applied patch to 'src/core/Sk2x.h' with conflicts.
  U src/core/Sk2x.h

Patch:       src/core/Sk2x.h
Index: src/core/Sk2x.h
diff --git a/src/core/Sk2x.h b/src/core/Sk2x.h
index
99cd45ebe80403177615e4cd4835305b690a0ae6..a95e281eed7db84e817e8a8dbe3828da762268ac
100644
--- a/src/core/Sk2x.h
+++ b/src/core/Sk2x.h
@@ -13,7 +13,7 @@
 #define SK2X_PREAMBLE 1
     #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
         #include "../opts/Sk2x_sse.h"
-    #elif defined(__ARM_NEON__)
+    #elif defined(SK_ARM_HAS_NEON)
         #include "../opts/Sk2x_neon.h"
     #else
         #include "../opts/Sk2x_none.h"
@@ -59,7 +59,7 @@ private:
 #define SK2X_PRIVATE 1
     #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
         #include "../opts/Sk2x_sse.h"
-    #elif defined(__ARM_NEON__)
+    #elif defined(SK_ARM_HAS_NEON)
         #include "../opts/Sk2x_neon.h"
     #else
         #include "../opts/Sk2x_none.h"
@@ -69,7 +69,7 @@ private:
 
 #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
     #include "../opts/Sk2x_sse.h"
-#elif defined(__ARM_NEON__)
+#elif defined(SK_ARM_HAS_NEON)
     #include "../opts/Sk2x_neon.h"
 #else
     #include "../opts/Sk2x_none.h"

[mtklein, 2015-03-20 15:02:47]

The CQ bit was checked by mtklein@google.com

[mtklein, 2015-03-20 15:02:48]

The patchset sent to the CQ was uploaded after l-g-t-m from reed@google.com
Link to the patchset: https://codereview.chromium.org/1020963002/#ps40001
(title: "rebase")

[commit-bot: I haz the power, 2015-03-20 15:03:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1020963002/40001

[commit-bot: I haz the power, 2015-03-20 15:32:40]

Committed patchset #3 (id:40001) as
https://skia.googlesource.com/skia/+/e57b5cab261a243dcbefa74c91c896c28959bf09

[mtklein, 2015-03-20 15:46:07]

A revert of this CL (patchset #3 id:40001) has been created in
https://codereview.chromium.org/1028523003/ by mtklein@google.com.

The reason for reverting is:
https://uberchromegw.corp.google.com/i/client.skia.compile/builders/Build-Mac...

https://uberchromegw.corp.google.com/i/client.skia.compile/builders/Build-Mac...

https://uberchromegw.corp.google.com/i/client.skia.compile/builders/Build-Ubu....

[mtklein, 2015-03-20 16:10:05]

The CQ bit was checked by mtklein@google.com

[mtklein, 2015-03-20 16:10:05]

The patchset sent to the CQ was uploaded after l-g-t-m from reed@google.com
Link to the patchset: https://codereview.chromium.org/1020963002/#ps80001
(title: "Avoid use of vset[q]_lane, instead intializing vectors directly.")

[commit-bot: I haz the power, 2015-03-20 16:10:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1020963002/80001

[commit-bot: I haz the power, 2015-03-20 16:25:30]

Committed patchset #5 (id:80001) as
https://skia.googlesource.com/skia/+/b79ff56de23fef680ae7187040f2d6a9516b553d