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.

NEWS

@@ -65,6 +65,21 @@ GNU Bison NEWS
   "function declared 'noreturn' should not return") have also been
   addressed.
 
+** New %define variable: api.location.type (glr.cc, lalr1.cc)
+
+  The %define variable api.location.type defines the name of the type to use
+  for locations.  When defined, Bison no longer generates the position.hh
+  and location.hh files, nor does the parser will include them: the user is
+  then responsible to define her type.
+
+  This can be used in programs with several parsers to factor their location
+  and position files: let one of them generate them, and let the others
+  simply resue these types and files.
+
+  This feature was actually introduced, but not documented, in Bison 2.5,
+  under the name "location_type" (which is maintained for backward
+  compatibility).
+
 * Noteworthy changes in release 2.6.2 (2012-08-03) [stable]
 
 ** Bug fixes