A GList doesn't make much sense for storing guints, so
now a GArray is used internally.
gdk_touch_cluster_get_touches() has changed to return an
allocated guint*, and gdk_touch_cluster_get_n_touches()
has been added too.
gdk_touch_cluster_set_device() had to be called right after anyway,
so set the device directly within this call, and favor the most common
scenario where there's just 1 single multitouch device behind 1 master
device.
Now that GtkButton and GtkScale are multitouch approved, it's
sufficient to enable GDK_TOUCH_MASK on them to have them deal
with multitouch devices.
The scales set rgba of the currently selected rectangle, and
the button adds more rectangles, those can be manipulated
simultaneously together with the rectangles, the only limit
is the number of touches the touchscreen hw is able to detect.
