[automerger skipped] Merge "external/libvpx: cherry-pick -Wunreachable-code-loop-increment fix" am: 1b59bcbece -s ours

am skip reason: Change-Id Iab8a1037950a9b2c006bd18b638fce77add199e8 with SHA-1 8c3be56557 is in history

Change-Id: Idc5f5bc91fc481bdbf0daef2c0b5c69f70534015