The new reference.pnm is a freely licensed replacement. The photo has
been taken by Reinhard Tartler on August 28 2014, and is licensed under
the expat license as stated at http://www.jclark.com/xml/copying.txt

QuickTime will play multiple audio tracks concurrently if this flag is
set for multiple audio tracks.  And if no subtitle track has this flag
set, QuickTime will show no subtitles in the subtitle menu.
Signed-off-by: Anton Khirnov <anton@khirnov.net>

Signed-off-by: Mans Rullgard <mans@mansr.com>