Fix #6280 – region (first_frame()==0) selectable with SnapRegionBoundary

Issue #6280 states that when selecting ranges using SnapToRegionBoundary it's
not possible to select regions with first_frame() == 0. This is because
Playlist::find_next_region() does not consider region boundaries == pos but
only > pos. Thus it never considers pos == 0 to be a region boundary.

This solution tries to be as little invasive as possible without changing the
semantics of PlayList::find_next_region(). Therefore position 0 is added to the
region boundary cache if there's a region starting at position 0 in any track.

0 files changed, 0 insertions, 0 deletions