Fix refcount problem

* src/video_output/video_output.c: moved some stuff to vout_IntfInit().
* include/video_output.h: vout_vaControl()/vout_Control() prototypes.
* modules/video_output/x11/xcommon.c: implemented a vout_Control() (only VOUT_SET_ZOOM for now).
* modules/gui/wxwindows/menus.cpp: handle float object vars, added "zoom" to the menus.

 * share/skins2/default/skin.dtd: Changed a few details here and there

  audio PIDs

   + bookmarks menu.
   + started work on bookmarks dialog.
   + started support for embeddable vout (via vout_RequestWindow()/vout_ReleaseWindow()).   
   + new --wxwin-bookmarks and --wxwin-embed config options.

   + new input_Control() function (doesn't do much for now).
   + started bookmarks support through input_Control().
   + new --bookmarks={name=foo,bytes=foo,time=foo},{...} config option.

* src/video_output/*:
   + started support for embeddable vouts (vout_RequestWindow()/vout_ReleaseWindow())
   + new --video-x/y config options

  Fixes #1104

* modules/gui/skins2/Modules.am: removed old skins2 theme.

   This doesn't fix totally the refresh problems on the skinned vout,
   but it improves the situation a lot.

  * skin.dtd : new BitmapFont element

* modules/codec/libmpeg2.c: modified last change to use a 4:3 aspect ratio when libmpeg2 gives us an invalid one.
  (if this happens, it is a bug in libmpeg2 anyway so we just try to fallback to the most usual value).

 (There is still the problem of timeout, and a lot of checks aren't done).

  * parser/builder.cpp: a font with ID "defaultfont" is loaded from
  the common font directory

  * all: added a "tooltipfont" element in the <Theme> tag (unused at the
      moment)