qtdemux: Add basic support for MPEG-A stereoscopic video

qtdemux: Add basic support for MPEG-A stereoscopic video

The MPEG-A format provides an extension to the ISO base media
file format to store stereoscopic content encoded with different
codecs like H.264 and MPEG-4:2. The stereo video media information(svmi)
atom declares the presence and storage method for the video.

Stereo video information for MPEG-A can also be supplied through
the 'stvi' atom (ref: ISO/IEC_14496-12, ISO/IEC_23000-11), which
is not implemented in this patch.

Also missing is support for stereo video encoded as separate video tracks
for now.

Based on a patch by Sreerenj Balachandran <sreerenj.balachandran@intel.com>

https://bugzilla.gnome.org/show_bug.cgi?id=611157