Makes SDL-1.2 SDL_WM_GrabInput() non-blocking in case of SDL window is not
viewable. Patch provided by <pbonzini@redhat.com>.
See <http://bugzilla.libsdl.org/show_bug.cgi?id=1155>.

--- a/src/video/x11/SDL_x11wm.c	2007-12-31 04:48:13.000000000 +0000
+++ b/src/video/x11/SDL_x11wm.c	2009-01-15 10:27:14.000000000 +0000
@@ -351,13 +351,14 @@ SDL_GrabMode X11_GrabInputNoLock(_THIS, 
 			result = XGrabPointer(SDL_Display, SDL_Window, True, 0,
 						GrabModeAsync, GrabModeAsync,
 						SDL_Window, None, CurrentTime);
-			if ( result == GrabSuccess ) {
+			if ( result == GrabSuccess || result == GrabNotViewable ) {
 				break;
 			}
 			SDL_Delay(100);
 		}
 		if ( result != GrabSuccess ) {
 			/* Uh, oh, what do we do here? */ ;
+			return(SDL_GRAB_OFF);
 		}
 		/* Now grab the keyboard */
 		XGrabKeyboard(SDL_Display, WMwindow, True,
