Don't call XInput2 multitouch APIs if they aren't supported.
I think it fixes this:
http://forums.libsdl.org/viewtopic.php?t=8324&sid=ae797309f9e2084cadc1b6a7615bd0e4
1.1 --- a/src/video/x11/SDL_x11xinput2.c Mon Sep 17 19:20:47 2012 -0400
1.2 +++ b/src/video/x11/SDL_x11xinput2.c Mon Sep 17 19:25:42 2012 -0400
1.3 @@ -220,6 +220,10 @@
1.4 void
1.5 X11_Xinput2SelectTouch(_THIS, SDL_Window *window) {
1.6 #if SDL_VIDEO_DRIVER_X11_XINPUT2_SUPPORTS_MULTITOUCH
1.7 + if (!X11_Xinput2IsMultitouchSupported()) {
1.8 + return;
1.9 + }
1.10 +
1.11 SDL_VideoData *data = (SDL_VideoData *) _this->driverdata;
1.12 XIEventMask eventmask;
1.13 unsigned char mask[3] = { 0,0,0 };