server: Support for closing the desktop window.

If a thread is owning the desktop window, when all other users of the
desktop have exited, signal the owner to close the desktop (with a 1
second delay).
diff --git a/server/process.c b/server/process.c
index cc88c5f..824f9b3 100644
--- a/server/process.c
+++ b/server/process.c
@@ -570,6 +570,7 @@
 
     assert( list_empty( &process->thread_list ));
     gettimeofday( &process->end_time, NULL );
+    close_process_desktop( process );
     handles = process->handles;
     process->handles = NULL;
     if (handles) release_object( handles );