intl: Drop argz processing outside of glibc.
* gettext-runtime/intl/l10nflist.c: Don't test HAVE_ARGZ_H.
(__argz_count, __argz_stringify, __argz_next): Remove definitions.
(_nl_make_l10nflist): Simplify !_LIBC case.
* gettext-runtime/m4/intl.m4 (gt_INTL_SUBDIR_CORE): Don't test for <argz.h>,
argz_count, argz_stringify, argz_next.
