warnings: factoring: complaints

warnings: factoring: complaints

* src/complain.c (error_message): Accept warning categories (an integer) as
argument.
Location is a 'const location *' instead of 'location *'.
(ERROR_MESSAGE): Delete it.
* src/complain.c, src/complain.h (complains): New function.
(complain, complain_at, complain_at_indent): Generic functions for
complaints. Call 'complains'.
(warn_at, warn_at_indent, warn, yacc_at, midrule_value_at)
(fatal_at, fatal): Delete them. Adjust dependencies.
* src/complain.h (enum warnings): New fields 'complaint' and 'fatal'.
* bootstrap.conf (XGETTEXT_OPTIONS): Adjust.