renamed ordinal.* to ord.*

--- a/src/ZF/ROOT.ML	Mon Oct 11 12:35:00 1993 +0100
+++ b/src/ZF/ROOT.ML	Mon Oct 11 13:58:22 1993 +0100
@@ -54,7 +54,7 @@
 use_thy "perm";
 use_thy "trancl";
 use_thy "wf";
-use_thy "ordinal";
+use_thy "ord";
 use_thy "nat";
 use_thy "epsilon";
 use_thy "arith";