Suppression of "6 numbers" limit. New option to choose tree type.

best.c

@@ -43,8 +43,13 @@ int check_best(res, nops, node, values, ops)
     if (diff < bestdiff || (diff == bestdiff && nops < bestops)) {
         //best=res;
         // clear old bests
-        for (i=0; i<nbests; ++i)
-            free_node(bests[i].root);
+        for (i=0; i<nbests; ++i) {
+            found=free_node(bests[i].root);
+#           ifdef DEBUG_TREE
+            printf("check_best: freed %d nodes\n", found);
+#           endif
+        }
+
         bestdiff=diff;
         bestops=nops;
         nbests=0;