Mac OS X joystick support: don't ignore kHIDUsage_GD_MultiAxisController

devices, since they are probably joysticks, or joystick-like things.

See 3Dconnexion's SpaceNavigator for an example of such a device:
   http://www.3dconnexion.com/products/3a1d.php

Thanks to Laurence Passmore for the fix.

--HG--
branch : SDL-1.2

src/joystick/darwin/SDL_sysjoystick.c

@@ -652,7 +652,8 @@ int SDL_SYS_JoystickInit(void)
 		/* Filter device list to non-keyboard/mouse stuff */ 
 		if ( (device->usagePage != kHIDPage_GenericDesktop) ||
 		     ((device->usage != kHIDUsage_GD_Joystick &&
-		      device->usage != kHIDUsage_GD_GamePad)) ) {
+		      device->usage != kHIDUsage_GD_GamePad &&
+		      device->usage != kHIDUsage_GD_MultiAxisController)) ) {
 
 			/* release memory for the device */
 			HIDDisposeDevice (&device);