libvpx: Pull from upstream

Current HEAD: 8c03fff40b05fa231adf8b564de22f03e42814b7

git log from upstream:
8c03fff Move abs() to where it is effective

TBR=tomfinegan@chromium.org

Review URL: https://codereview.chromium.org/376873009

git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/libvpx@281854 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
2 files changed