cocoa: fix view leak in uninit when fullscreen
vo_opengl: clamp filters to their size

This gives better results with fancy-downscaling. The issue here is that
fancy-downscalign "extends" the filter radius by some amount, which
requires using a larger filter size and shader. Then most of the filter
is "unused", but some filters still return non-0 coefficients, which
create heavy artifacts. Just clamp them off.

I'm not sure if this is the right solution, but at least it's better
than before.
vo_opengl: extend filter size to 64

For better downscaling.

Maybe the list of filter sizes shouldn't be static...
player: when seeking past EOF with --keep-open, seek to last frame

It feels strange that seeking past EOF with --keep-open actually leaves
the player at a random position. You can't even unpause, because the
demuxer is in the EOF state, and what you see on screen is just what was
around before the seek.

Improve this by attempting to seek to the last video frame if EOF
happens. We explicitly don't do this if EOF was reached normally to
increase robustness (if the VO got a frame since the last seek, it
obviously means we had normal playback before EOF).

If an error happens when trying to find the last frame (such as not
actually finding a last frame because e.g. the demuxer misbehaves), this
will probably turn your CPU into a heater. There is no logic to prevent
reinitiating the last-frame search if the last-frame search reached EOF.
(Pausing usually prevents that EOF is reached again after a successful
last-frame search.)

Fixes #819.
sub: remove assertion

This should clearly be impossible, but it seems to happen with ordered
chapters for a user.

Since I can't tell what the actual bug is and it seems impossible to
know the details without downloading possibly huge files, this is
probably the best we can do.

Should at least partially fix #1319.
options: add a 'once' idle mode

This allows to make mpv wait for file open events at start but close
after it is done playing the first playlist.
cocoa: bundle: use idle=once