* tests/gpgscm/scheme-private.h (struct port): Move location
information out of the union.
* tests/gpgscm/scheme.c (mark): All ports need marking now.
(gc): Likewise all ports on the load stack.
(port_clear_location): Adapt accordingly.  Also, add an empty function
for !SHOW_ERROR_LINE.
(port_increment_current_line): Likewise.
(port_reset_current_line): Drop function in favor of...
(port_init_location): ... this new function.
(file_push): Simplify.
(file_pop): Likewise.
(port_rep_from_filename): Likewise.
(port_rep_from_file): Likewise.
(port_rep_from_string): Also initialize the location.
(port_rep_from_scratch): Likewise.
(port_close): Simplify and generalize.
(skipspace): Likewise.
(token): Likewise.
(_Error_1): Generalize.
(opexe_5): Likewise.
(scheme_deinit): Simplify and generalize.
(scheme_load_named_file): Likewise.
(scheme_load_string): Also initialize the location.