VeNum optimizations to libpng to improve PNG decode time

Set correct counter in neon routine for SUB filter type.
Enable Neon optimizations for all filter types and pixel depths.

Change-Id: Ica0d39e828a9e0cba59cbc3632830e4eb3e59607
(cherry picked from commit b912f64bc4bb174fc055cda58e303faaa640b8b1)

Conflicts:

	pngrutil.c

Conflicts:
	Android.mk