lalr1.cc: location.hh and position.hh are not generated without %defines

lalr1.cc: location.hh and position.hh are not generated without %defines

* data/location.cc (b4_position_define, b4_location_define): New.
(location.hh, position.hh): Generate only if %defines.
* data/lalr1.cc: therefore, define these classes when locations are
needed, but headers are not generated.
* tests/output.at: Check that these files are not generated.
* NEWS: Document.