This patch adds a new static function get_qt_codec() that takes care of
the initial retrieval of the fourcc and codec ID for A_QUICKTIME and
V_QUICKTIME. It also normalizes noncompliant private data found in some
older files that incorrectly starts with the fourcc by expanding/shifting
the data by 4 bytes, and storing the data size at the start. This is
necessary in order for the rest of the code in the A_QUICKTIME and
V_QUICKTIME blocks (and most likely other code as well) to correctly
parse the private data.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>