Xi: allocate motion history for master device.

We're still missing out on the actual content of the history but at least this
way we don't segfault.

Xi/exevents.c

@@ -338,6 +338,7 @@ DeepCopyDeviceClasses(DeviceIntPtr from, DeviceIntPtr to)
             FatalError("[Xi] no memory for class shift.\n");
         memcpy(v, from->valuator, sizeof(ValuatorClassRec));
         v->motion = NULL;
+        AllocateMotionHistory(to); /*XXX should be copied somehow */
 
         v->axes = (AxisInfoPtr)&v[1];
         memcpy(v->axes, from->valuator->axes, v->numAxes * sizeof(AxisInfo));