Disable by default the code that forcefully moved the video output
window to the middle of the screen whenever it was reconfigured or
created. That behavior was really annoying when switching video
streams within a file, and overriding the window manager like that is
not good default behavior for the initial creation of a window either.
Add a new option "-force-window-position" that can be used to restore
the old behavior.
Name the field "sub_id" as it's not specific to DVD subs.
Remove some other unused extern declarations together with dvdsub_id
from demux_mkv.c and demux_lavf.c.
Add a 'struct vo *vo' argument to the x11_common.c functions that
access the variable so it's available as vo->opts->vo_ontop. To keep
VOs using the old API working create a global vo variable that is set
to the currently used old vo. "vo_ontop" will be #defined to
"global_vo->opts->vo_ontop", and x11_common.h will add defines like
the following when it is included by old VOs:
#define vo_x11_ontop() vo_x11_ontop(global_vo)
so that they will call the function according to the new declaration.
First part of option restructuring. The aim is to move option values
from a huge number of separate globals to a single non-global struct.
This part adds some support for parsing option values into such struct
instances, and moves one example option (fixed-vo) to the struct.
