dropped obsolete ROOT.ML

--- a/src/HOL/Import/ROOT.ML	Sat Mar 03 22:38:53 2012 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,5 +0,0 @@
-(*  Title:      HOL/Import/ROOT.ML
-    Author:     Sebastian Skalberg (TU Muenchen)
-*)
-
-use_thys ["HOL4Compat", "HOL4Syntax"];