reverted c05d3e22adaf: Locale.intern is still required by AFP/Simpl;

--- a/src/Pure/Isar/locale.ML	Mon Feb 24 19:44:09 2014 +0100
+++ b/src/Pure/Isar/locale.ML	Mon Feb 24 20:42:08 2014 +0100
@@ -36,6 +36,7 @@
     declaration list ->
     (string * (Attrib.binding * (thm list * Attrib.src list) list) list) list ->
     (string * morphism) list -> theory -> theory
+  val intern: theory -> xstring -> string
   val check: theory -> xstring * Position.T -> string
   val extern: theory -> string -> xstring
   val markup_name: Proof.context -> string -> string
@@ -159,6 +160,7 @@
   val merge = Name_Space.join_tables (K merge_locale);
 );
 
+val intern = Name_Space.intern o #1 o Locales.get;
 fun check thy = #1 o Name_Space.check (Context.Theory thy) (Locales.get thy);
 
 fun extern thy = Name_Space.extern (Proof_Context.init_global thy) (#1 (Locales.get thy));