[NORMATIVE] Allow padding bytes at the end of each OBU
[NORMATIVE] Allow padding bytes at the end of each OBU

Accept OBUs which contain trailing 0 bytes after the payload
and trailing '1' bit. We check that these extra bytes are all
zero, so that we can catch cases where we really have decoded
less data than expected.

BUG=aomedia:1666

Change-Id: I77114a7f86e1e01deaace0ad5ea0e27d9717d488

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom