mplayer: change default window size for --force-window

Closer to the ubiquitous 16:9 screen aspect ratio. Requested by ChrisK3.
mplayer: make VO interaction work in --idle mode

Didn't handle VO events, didn't handle OSD message management.

There is probably still some strangeness left. --idle mode was never
made for direct interaction.
mplayer: osd bar depends on VO, not video decoding

The OSD bar wasn't displayed, and instead a fallback message was shown.
vo: mark frame lost after seek reset

Reverts a small change made in commit ed9295c. This is needed, because
otherwise mplayer.c/update_video_attached_pic() thinks it never has to
update the picture after initialization. (Maybe there would be more
elegant ways to handle this, but not without adding extra state.)
command: don't let "avsync" property print NOPTS value

Can happen when seeking in audio files with attached picture.
MP_NOPTS_VALUE doesn't really make sense outside of mpv internals, so
don't return it.
input: remove strange offset from commands enum

A leftover from 10 years of refactoring.
command: add sub_seek input command

Essentially reuses the sub_step command, and is subject to the same
restrictions.

Seems to behave a bit strange sometimes, but generally works.
cosmetics: replace "CTRL" defines by enums

Because why not.
vo_opengl_old: mp_msg conversion

This was the only thing in video/out/ left with major mp_msg() use.