This feeds into efforts to create a working install target.
The order of headers is still funky, and was "fixed" by clang-format,
but in a way that doesn't exactly align with the style guide. Further
cleanup of header order is coming in a follow-up PR.
Implemented according to bitstream spec at
https://aomediacodec.github.io/av1-spec/.
It will be used to do AV1 subsample encryption later.
Issue #453.
Change-Id: I84d8a2a780d95f2c9f430ee598838b97474cc0af
Joey Parrish
Cosmin Stejerean
Carlos Bentzen
KongQun Yang