+ *
+ * XXX We can probe /var/run/dmesg.boot which is world-readable.
+ * XXX This would be somewhat system-dependant, but is doable.
+ * XXX E.g., on NetBSD, my USB mouse registers:
+ * XXX ums0 at uhidev0: 3 buttons and Z dir.
+ * XXX We can also probe /var/log/XFree86\..*\.log to get
+ * XXX lines such as:
+ * XXX (**) Option "Buttons" "5"
+ * XXX (**) Option "ZAxisMapping" "4 5"
+ * XXX (**) Mouse0: ZAxisMapping: buttons 4 and 5
+ * XXX (**) Mouse0: Buttons: 5
+ * XXX ...which tells us even more, and is a bit less
+ * XXX system-dependant. (Other than MS-WINDOWS, all
+ * XXX target hosts with actual users are probably running
+ * XXX XFree86...) It is at least worth taking a look at
+ * XXX this file.