libvpx: Pull from upstream

Current HEAD: 79b88cc2a57a9c27bf12e053204dbc5d0c141ec6

git log from upstream:
6d7b7ab Add non420 code in multi-threaded loopfilter
f5bbe24 Fix obvious misses in doxygen mainpage
e76eaf0 vp9_ethread: add parallel loopfilter
a6715a7 Add vp9_highbitdepth info in configure --help
cc2da09 Fix variance Neon intrinsics > 32x32
dfda5ce Fix frame buffer swap in denoiser
220bc3a [two pass temporal svc]Fix crash issue in transcoder app caused by last fix.
1be4267 Fix color_space enum comments for doxygen
7ef157c Fix doxygen warning with usage.dox
1b7391a Remove obsolete doxygen tags
9ace4f9 Fix comments for doxygen
99b9983 Align thread data in vp9_ethread
6f4d29c Clarify purpose of VP9_INVERT_TILE_DECODE_ORDER
3ca15a8 Add comments for two SVC related controls
193ca4b Add comments for two SVC related controls
dc08b20 Add comments for control VP9E_SET_TUNE_CONTENT
4ab39e1 Add comments for VP9E_SET_FRAME_PERIODIC_BOOST
87c436f Fix comments for encoder controls
e94b415 Add encoder control for setting color space
588f74f Switch remaining Neon variance functions to shifts
ec1d838 Add 64x64 sub_pel_variance Neon function
6b223fc Enable decoder to pass through color space info
74d40cd Add 64x variance Neon functions
a14415d [twopass temporal svc] Fix decoding error on seek.
ce52b0f Added plumbing for setting color space
7cb111b Unit test for turning VP8 denoiser on/off periodically.
2c6d9c5 vp8: Fix to crash in pick_inter.
ecbca31 Fix comments and color format

TBR=tomfinegan@chromium.org

Review URL: https://codereview.chromium.org//800493003
53 files changed