* src/video_output/vout_intf.c, include/video_output.h:

* src/video_output/vout_intf.c, include/video_output.h:
  + vout_RequestWindow() will now cycle through all the available interfaces until
it finds one with embedded vout support.
    This fixes the issue where embedded vout would stop working when additional
interfaces are spawned after the main interface is started.
  + vout_RequestWindow() now stores the parent interface pointer into the vout
object for later use by vout_ControlWindow() and vout_ReleaseWindow().
  + added a vout_vaControlDefault() called by the vouts pf_control() when they
don't handle something.
* modules/video_output/directx/events.c, modules/video_output/x11/xcommon.c:
  + call vout_vaControlDefault().
* modules/gui/wxwindows/wxwindows.cpp: sets p_intf->b_dead when the interface is
about to be destroyed.