Add optimization of Skia S32A_Blend blitter

Adds optimization of Skia S32A_Blend_BlitRow32 blitter using ARM NEON
instruction set. Special cases for when pixel alpha is zero.
Improves performance platform wide.

Change-Id: I6c8bf8a9525838682206ebd139855354d6b3a563
Signed-off-by: Henrik Smiding <henrik.smiding@stericsson.com>
Signed-off-by: Patrik Ryd <patrik.ryd@stericsson.com>

Conflicts:
	Android.mk