Currently it was only using stubs. Let's actually translate the
strings using gettext.
* examples/c/bistromathic/local.mk: Define LOCALEDIR, BISON_LOCALEDIR
and link with libintl.
* examples/c/bistromathic/parse.y: Use them.
Remove useless includes.
Take ENABLE_NLS into account.
(error_format_string): New.
(yyreport_syntax_error): Rewrite to rely on a format string, which is
more appropriate for internationalization.
* examples/c/bistromathic/Makefile: We no longer use Flex.
We need readline and intl.
* doc/bison.texi: Point to bistromathic for a better option for
internationalization.
* po/POTFILES.in: Add bistromathic.