+ * 2005-05-31: An addendum to the above. Some games might want
+ * a `priority order' among buttons, such that if one button is
+ * pressed while another is down then a fixed one of the
+ * buttons takes priority no matter what order they're pressed
+ * in. Mines, in particular, wants to treat a left+right click
+ * like a left click for the benefit of users of other
+ * implementations. So the last of the above points is modified
+ * in the presence of an (optional) button priority order.