Skia: Add NEON intrinsic D32_A8_Black and D32_A8_Opaque
Skia: Add NEON intrinsic D32_A8_Black and D32_A8_Opaque

If NEON support is indiciated via __ARM_HAVE_NEON flag then use
an optimized NEON intrinsics version of the D32_A8_Black and D32_A8_Opaque
masking function.

Change-Id: I20d2bf15515d960b73e635784a0daf29302e1f12

VRToxin-AOSP/android_external_skia,VRToxin-AOSP/android_external_skia,VRToxin-AOSP/android_external_skia,VRToxin-AOSP/android_external_skia,VRToxin-AOSP/android_external_skia,VRToxin-AOSP/android_external_skia,VRToxin-AOSP/android_external_skia,VRToxin-AOSP/android_external_skia,VRToxin-AOSP/android_external_skia