SCUMM: Allow Alt-x to be used to quit SCUMM games.

This includes a TODO to check which SCUMM games actually exhibit this behavior
originally. cbd8673 added this behavior to our
backend code initially.

NEWS

@@ -65,6 +65,7 @@ For a more comprehensive changelog of the latest experimental code, see:
    - Implemented original Maniac Mansion v0-v1 walking code.
    - It is now possible to play Maniac Mansion from within Day of the
      Tentacle, with a few caveats. See README for details.
+   - Alt-x can now be used to quit SCUMM games on all platforms.
 
  Tinsel:
    - Improved AdLib music support in Discworld 1.

README

@@ -1505,6 +1505,7 @@ other games.
                              of the middle mouse button or wheel.
 
   SCUMM:
+    Alt-x                  - Quit
     Ctrl 0-9 and Alt 0-9   - Load and save game state
     Ctrl-d                 - Starts the debugger
     Ctrl-f                 - Toggle fast mode

engines/scumm/input.cpp

@@ -130,6 +130,14 @@ void ScummEngine::parseEvent(Common::Event event) {
 			_debugger->attach();
 		} else if (event.kbd.hasFlags(Common::KBD_CTRL) && event.kbd.keycode == Common::KEYCODE_s) {
 			_res->resourceStats();
+		} else if (event.kbd.hasFlags(Common::KBD_ALT) && event.kbd.keycode == Common::KEYCODE_x) {
+			// TODO: Some SCUMM games quit when Alt-x is pressed. However, not
+			// all of them seem to exhibit this behavior. LordHoto found that
+			// the Loom manual does not mention this hotkey. On the other hand
+			// the Sam&Max manual mentions that Alt-x does so on "most"
+			// platforms. We should really check which games exhibit this
+			// behavior and only use it for them.
+			quitGame();
 		} else {
 			// Normal key press, pass on to the game.
 			_keyPressed = event.kbd;