glr: do not use locations when they are not requested

glr: do not use locations when they are not requested

When the test suite runs with -O2 and warnings enabled, G++
complains of locations being used, but not initialized.
The simplest is to not use locations.

* data/glr.c (b4_locuser_formals, b4_locuser_args): New.
Use them when locations should not be used.
Use b4_locations_if where appropriate.
(yyuserAction): Modify the order to the arguments to make
it more alike the other routines, and to make use of
b4_locuser_args simpler.