clarified split_thy_path;

--- a/src/Pure/Thy/thy_header.scala	Thu Jan 13 17:27:52 2011 +0100
+++ b/src/Pure/Thy/thy_header.scala	Thu Jan 13 17:30:52 2011 +0100
@@ -30,7 +30,7 @@
   /* file name */
 
   val Thy_Path1 = new Regex("([^/]*)\\.thy")
-  val Thy_Path2 = new Regex("(.*/)([^/]*)\\.thy")
+  val Thy_Path2 = new Regex("(.*)/([^/]*)\\.thy")
 
   def split_thy_path(path: String): Option[(String, String)] =
     path match {