x11: Prevent leak on XIQueryDevice

Per http://linux.die.net/man/3/xiquerydevice:

> XIFreeDeviceInfo frees the information returned by
> XIQueryDevice.

src/api/x11/input.rs

@@ -315,6 +315,10 @@ fn read_input_axis_info(display: &Arc<XConnection>) -> Vec<Axis> {
         }
     }
 
+    unsafe {
+        (display.xinput2.XIFreeDeviceInfo)(devices);
+    }
+
     axis_list
 }