c++: api.location.type

c++: api.location.type

This feature was introduced in 95a2de5695670ae0df98cb3c42141cad549f0204
(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.