updated the identifier "version"

--- a/src/Pure/ROOT.ML	Tue Sep 13 10:26:24 1994 +0200
+++ b/src/Pure/ROOT.ML	Tue Sep 13 10:42:34 1994 +0200
@@ -12,7 +12,7 @@
 *)
 
 val banner = "Pure Isabelle";
-val version = "October 93";
+val version = "Isabelle-94: September 94";
 
 print_depth 1;