Updating the libav submodule to the latest upstream master branch commit.
Updated the CHANGELOG with progress so far.  Created an UPGRADING file to list additions, deprecations, and removals.
Increased the parallel option for make from -j4 to -j9, since my new laptop has 8 cores.  Removed a duplicate configure flag.
Fixed AVbinInfo.version to be exactly the same type of integer as others of its type.  Fixed the definition of avbin_stream_info() so it matches the declaration of it in avbin.h and the actual behaviour.