This commit introduces a parser for the current bitstream produced by
Daala. It currently bears a large similarity with Theora, another
codec produced by Xiph. While likely to change in the future, its basic
format of packet parsing should remain fairly identical with its current
structure.
Once the bitstream freezes, there are a few probable simplifications
that could be made. Also, the current version (major, minor and micro)
is stuck at zero so it's unusable as a way to warn about possible
incompatibilities. This will change once the bitstream freezes,
however until then this file is strictly targeting the current git
master of the reference encoder, libdaala.

This file was developed independently at the same time by both myself
and Vittorio Giovara, who used libav as a starting point. For fairness,
and to prevent confusion and allegations, his name has been added to the
copyright in the license header as well, and vice versa.