bump libmp4v2 r224 ->r286; chunk duration; tags; cover-art

bump libmp4v2 r224 ->r286; chunk duration; tags; cover-art

The major changes to libmp4v2 include the new Tags API for iTunes metadata management
and new API to set track chunk duration limits. Additionally, the patches for libmp4v2
are no longer required and libmp4v2 should build significantly faster as it now
enabled precompiled headers on various platforms.

Tags API effects common.h, decmetdata.c and muxmp4.c and replaces the operations in
a near 1:1 mapping for functionality except all access happens in between alloc/fetch
and store/free pattern.

libhb no longer checks the bits of cover-art in order to determine image type. That
functionality is now delegated to libmp4v2; and libhb identify_art_type() has been
removed accordingly.

Chunk duration support has been added which makes use of new API from libmp4v2:

    MP4SetTrackDurationPerChunk( MP4File, MP4TrackId );

And muxmp4 adds new internal function MP4TuneTrackDurationPerChunk() which is
invoked after all video/audio track creation which tunes chunk duration to the
equivalent of 4-frames in track timescale; as per van's suggestion.

git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@2347 b64f7644-9d1e-0410-96f1-a4d463321fa5