c++: api.location.type

This feature was introduced in 95a2de5695
(which is part of 2.5), but not documented.  Give it a proper name, and
make it public.

* data/c++.m4, data/lalr1.cc, data/glr.cc, data/java.m4: Use
api.location.type instead of location_type.
* src/muscle-tab.c (muscle_percent_variable_update): Map the latter to
the former.
* tests/local.at: Adjust.
* tests/calc.at: Use api.location.type.
Leave tests/java.at with location_type, at least for the time being,
to cover both names.
* doc/bison.texi: Document api.location.type.
(User Defined Location Type): New.
* NEWS: Update.

data/lalr1.cc

@@ -24,7 +24,7 @@ m4_define([b4_parser_class_name],
 b4_defines_if([],
               [b4_fatal([b4_skeleton[: using %%defines is mandatory]])])
 
-b4_percent_define_ifdef([[location_type]], [],
+b4_percent_define_ifdef([[api.location.type]], [],
   [# Backward compatibility.
   m4_define([b4_location_constructors])
   m4_include(b4_pkgdatadir/[location.cc])])
@@ -52,7 +52,7 @@ b4_copyright([Skeleton interface for Bison LALR(1) parsers in C++],
 #include <string>
 #include <iostream>
 #include "stack.hh"
-]b4_percent_define_ifdef([[location_type]], [],
+]b4_percent_define_ifdef([[api.location.type]], [],
                          [[#include "location.hh"]])[
 
 ]b4_YYDEBUG_define[
@@ -77,7 +77,7 @@ b4_user_stype
     typedef ]b4_api_PREFIX[STYPE semantic_type;
 #endif
     /// Symbol locations.
-    typedef ]b4_percent_define_get([[location_type]],
+    typedef ]b4_percent_define_get([[api.location.type]],
                                    [[location]])[ location_type;
     /// Tokens.
     struct token