Upgrade to the latest version of libvpx pulled from the webm project's git server.

latest commit pulled from git://review.webmproject.org/libvpx.git:
    82315be75d54d00ad5f2ea51f844f27f2d921dc0

Also enabled more optimizations in the neon build.

Change-Id: I744765d798471c30c2faf32af27161f772129516
286 files changed