service discovery and demux modules.

   isn't really efficient)

* src/video_output/*: re-implemented InitWindowSize() using fmt_in.i_sar_num/den and moved it to vout_intf.c where it can be called again after crop or aspect ratio changes.

* src/libvlc.h, src/video_output/vout_intf.c: added crop config option + changed --monitor-aspect-ratio into --monitor-par (pixel aspect ratio). It makes a lot more sense since lots of widescreens still have square pixels.

* modules/video_output/directx/directx.c, modules/video_output/directx/glwin32.c, modules/video_output/opengl.c: support on-the-fly aspect-ratio changes.

plugin.cpp: on activation, set width and height in VLC configuration variables with plugin actual geometry, this prevents video rescaling when starting video

mkv.cpp: get ready to support pixel cropping (top/bottom/left/right) when it will work from the demuxer in VLC

* modules/video_output/x11/xcommon.c, modules/video_output/opengl.c, modules/video_filter/deinterlace.c: added on-the-fly cropping support to opengl and deinterlace.

--sout-udp-ttl takes precedence over -ttl