This avoids clearing the queued frame and the currently displayed one on
VO reconfiguration requests that happen when new frames arrive. Instead,
let those frames be fully displayed.
Fixes mf:// playback issues introduced after commit ef11d31.
Instead of removing the frame timing check embrace and fix it to wake up
the playloop as needed. The frame display duration is problematic to
handle as both VO and playloop thread would already be sleeping, but in
certain use cases it is needed to display frames in full, so in this
case, let the VO sleep to the end of frame, wake up the core as
requested and go back sleeping.
Note that this patch series reintroduces 0c9ac5835, which is esenitally
fixed in this commit. It is still not perfect, but it is better than
just busy waiting on playloop, even if those events when this would be
needed are quite rare.