Some fixes to the code to support running on an externally

supplied window.

SDL (at least recent 1.2.x versions) has the ability to run the
graphic output into an externally supplied window, whose ID in the
environment variable SDL_WINDOWID. Ideally, applications should
run unchanged irrespective of who creates the window. Unfortunately,
SDL does not subscribe to mouse, key and resize events on externally
supplied windows, so we need to do ask for these events explicitly.
 
On passing, also add some code to handle SDL_ACTIVEEVENT so if
the X11 window is killed while we are active, we call
"stop now" to terminate the asterisk instance.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@117052 65c4cc65-6c06-0410-ace0-fbb531ad65f3