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.
cherry picked from commit b912f64bc4bb174fc055cda58e303faaa640b8b1

Change-Id: I4ff1c78637db1ab91689ad90da9b5e7da07d2a9e
Update copyright to The Linux Foundation

Change-Id: I537e53b3bb9145aabb60dc482c495118d1f06b03
libpng: Fix for memory leak while indexing the PNG images

de-allocating the index resorces at proper place. png_read_destroy()
making png_ptr->index NULL and due to this de-allocation was not
happening even though code exist (it was like dead-code).

Change-Id: I770bbfc486365b1a8b6a8dc5f128aa2b3a34cd50
CRs-Fixed: 551617