This parameter has been unused for years (the last flag was removed in
commit d658b115). Get rid of it.
This affects the general VO API, as well as the vo_opengl backend API,
so it touches a lot of files.
The VOFLAGs are still used to control OpenGL context creation, so move
them to the OpenGL backend code.
Now among other things panscan can be changed during playback.
Unfortunately, it flickers. The issue is that reconfig() clears the
framebuffer. Removing the clearing shows that the "unused" parts of
the picture are not cleared - even though OSD could render there. As
such, this is a separate issue.
When running with --panscan=1, this could crash - because the current
frame was reduced in size each time the image was redrawn, which would
result in a failed assertion the second time it's drawn.
If user switched terminals frantically, mpv could get SIGUSR1 twice in a
row, which, up until now, resulted in destroying CRTC twice. This caused
it to segfault. After this fix, double SIGUSR1 should be ignored.
Logging was meant to be silenced only when user uses connector
auto-detection feature. If user supplies connector ID manually, he
should see exact reason why connecting to this specific connector
failed.
