[automerger skipped] Merge "external/libvpx: cherry-pick -Wunreachable-code-loop-increment fix" into stage-aosp-master am: affd87a4b0 -s ours

am skip reason: Change-Id Iab8a1037950a9b2c006bd18b638fce77add199e8 with SHA-1 1feae85011 is in history

Change-Id: I5c3a7e4ed23c2e007e2220eb1c323e7b8eba65d7