Add optimized S32A_D565_Opaque_Dither blitter.

Adds optimization of Skia S32A_D565_Opaque_Dither blitter using
ARM NEON instruction set.
Improves performance in browser.

Change-Id: Ie20fb3cf3ad9a60f01b79e3ed2ddba7651bcf013
Signed-off-by: Henrik Smiding <henrik.smiding@stericsson.com>
Signed-off-by: Patrik Ryd <patrik.ryd@stericsson.com>