Added comment.

--- a/src/Provers/classical.ML	Thu Apr 06 11:14:51 1995 +0200
+++ b/src/Provers/classical.ML	Thu Apr 06 11:55:51 1995 +0200
@@ -176,7 +176,9 @@
   writeln"Safe elimination rules";  prths safeEs;
   ());
 
-(** Adding new (un)safe introduction or elimination rules **)
+(** Adding new (un)safe introduction or elimination rules 
+    In case of overlap, new rules are tried BEFORE old ones
+**)
 
 fun (CS{safeIs,safeEs,hazIs,hazEs,wrapper,...}) addSIs ths =
   make_cs {safeIs=ths@safeIs,