When playing a loop, and if no end of loop point has been defined
(meaning = play whole segment), don't rely on segment's length for
wave tracks as their length is always 1.  Compute segment length in
this case by grabbing each track's playback length in segment state's
internal graph.  This feature is only activated for messages generated
by wave tracks, but could be extended if needed to other types of
messages.
Signed-off-by: Eric Pouech <epouech@codeweavers.com>