tuned simplifier trace output; new flag debug_simp

--- a/NEWS	Fri Oct 22 20:23:40 1999 +0200
+++ b/NEWS	Fri Oct 22 20:24:08 1999 +0200
@@ -287,6 +287,8 @@
 
 *** Internal programming interfaces ***
 
+* tuned simplifier trace output; new flag debug_simp;
+
 * structures Vartab / Termtab (instances of TableFun) offer efficient
 tables indexed by indexname_ord / term_ord (compatible with aconv);