- Cleaned up heuristic code. Note that there is a "hidden" heuristic:

implicitly, older goals are resolved first, if some goals have equal
  weights. This is encoded in the "w <=" comparison; if this is set to
  "w <", the heuristic becomes much less effective.

src/arachne.c

@@ -1946,7 +1946,7 @@ iterate ()
 		   * Check whether its a final state (i.e. all goals bound)
 		   */
 
-		  b = select_goal (sys);
+		  b = (Binding) select_goal (sys);
 		  if (b == NULL)
 		    {
 		      /*