Now loads deriv.ML

--- a/src/Pure/ROOT.ML	Wed Mar 20 18:43:08 1996 +0100
+++ b/src/Pure/ROOT.ML	Thu Mar 21 11:04:36 1996 +0100
@@ -35,6 +35,8 @@
 use "logic.ML";
 use "theory.ML";
 use "thm.ML";
+use "deriv.ML";
+use "display.ML";
 use "drule.ML";
 use "tctical.ML";
 use "search.ML";