disabled some code generation (an intermeidate solution)

--- a/src/HOL/Extraction/Higman.thy	Tue Oct 31 09:28:56 2006 +0100
+++ b/src/HOL/Extraction/Higman.thy	Tue Oct 31 09:28:57 2006 +0100
@@ -337,7 +337,7 @@
 end;
 *}
 
-code_gen good_prefix (SML -)
+(*code_gen good_prefix (SML "~/gen_code/higman.ML")
 
 ML {*
 local
@@ -383,6 +383,6 @@
 val xs4 = good_prefix f2;
 
 end;
-*}
+*}*)
 
 end