x11: remove a duplicated line
x11: request and handle resize events of parent windows with --wid

Before this commit, this was somehow polled (i.e. not the right way).

Also, selects the correct window when doing --wid=0 (which is another
weird special-case).
x11: always check whether a window exists

So any VOCTRL can be called at any time. Working towards removing all
these config_ok checks in vo.c.
demux_subreader: remove support for some subtitle formats

Drop: sami, vplayer, rt, pjs, mpsub, aqt, jacosub. None of these seem to be actually in use, except sami. Sami is very complex, and the results subreader produces are not very useful.

For all these formats, there are still parsers in FFmpeg. We remove the
subreader implementation, because it might contain security relevant
bugs and such. (This is old, unmaintained C string parsing code, written
in times where absolutely nobody cared about security. The kind of
awesome code.)

We keep the other formats, because they're (mostly) commonly used and
relatively simple, for UTF16 support (still missing in FFmpeg), and for
the sake of Libav.