libvpx: Pull from upstream

libvpx: Pull from upstream

Add support for avx2 intrinsics

Pass '-chromium' to ads2gas scripts. This allows us to generate
the correct syntax for Chromium clang as well as Xcode clang.
https://code.google.com/p/webm/issues/detail?id=603

Current HEAD: 4a535efcfd6c2d1ccded864faf042f4b78716206

git log from upstream:
4a535ef Change in data rate test to be less stringent
fbada94 Add frame buffer lru cache.
d0ee1fd Merge "Add support to pass in external frame buffers."
10f8916 Add support to pass in external frame buffers.
c5aaf92 webmdec/tests: fix leak when file isn't read to eof
64cf398 Merge "Using MV struct instead of int_mv union in encoder."
33df4f0 Merge "vp9_convole.c cleanup."
f54b515 Merge "Cleaning up vp9_append_sub8x8_mvs_for_idx()."
25da21b Using MV struct instead of int_mv union in encoder.
d4b500d Merge "Increase disable_filter_search_var_thresh threshold"
ec79db6 Merge "obj_int_extract: fix compile warning"
3aa75bc Merge "vp9 asserts: fix compile warning"
a793cf9 Merge "Rename so -> scan_order in vp9_encodemb.c"
df13e01 Merge "Renaming treed_write() to vp9_write_tree()."
15a23c8 Merge "zz_motion_search() cleanup."
33859ad Merge "Moving mi configuration loop from vp9_read_mode_info to set_offsets."
2f9d118 Merge "Remove some dead code"
930ae71 Rename so -> scan_order in vp9_encodemb.c
da9f55c Increase disable_filter_search_var_thresh threshold
2ec473b Merge "Set rc_2pass_vbr_maxsection_pct to correct value"
8b73296 Merge "Enable adaptive pred filter type for sub8x8"
15cf596 Set rc_2pass_vbr_maxsection_pct to correct value
e121bf4 Moving mi configuration loop from vp9_read_mode_info to set_offsets.
178db94 vp9 asserts: fix compile warning
934f0fb obj_int_extract: fix compile warning
3b5a90b Enable adaptive pred filter type for sub8x8
c263418 Merge "test-data.sha1: add missing sha1sums"
52bf934 zz_motion_search() cleanup.
629fb85 vp9_convole.c cleanup.

TBR=tomfinegan@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=240981

[Johann, 2013-12-16 19:49:45]

Committed patchset #1 manually as r240981 (presubmit successful).

[Tom Finegan, 2013-12-16 20:22:47]

On 2013/12/16 19:49:45, Johann wrote:
> Committed patchset #1 manually as r240981 (presubmit successful).

lgtm/rubber stamp