export parser for "-"

--- a/src/Pure/Isar/outer_parse.ML	Mon May 16 08:28:16 2005 +0200
+++ b/src/Pure/Isar/outer_parse.ML	Mon May 16 09:34:20 2005 +0200
@@ -21,6 +21,7 @@
   val short_ident: token list -> string * token list
   val long_ident: token list -> string * token list
   val sym_ident: token list -> string * token list
+  val minus: token list -> string * token list
   val term_var: token list -> string * token list
   val type_ident: token list -> string * token list
   val type_var: token list -> string * token list