Simplify Autoconf macros.
* gettext-runtime/m4/intldir.m4: Remove file.
* gettext-runtime/m4/Makefile.am (EXTRA_DIST): Remove intldir.m4.
* gettext-runtime/m4/gettext.m4 (AM_GNU_GETTEXT): Disallow 'no-libtool'
argument. Use libtool always. Remove variables that existed only for backward
compatibility.
* gettext-runtime/m4/intl.m4: Update comments.
* autogen.sh: Ignore gettext.m4 and intl.m4 from gnulib.
* gettext-runtime/intl/Makefile.in: Use libtool always.
(libintl.a, libgnuintl.a): Remove rule.
(.o): Remove suffix rule.
(install-exec, installdirs, uninstall, distclean, dist, distdir): PACKAGE cannot
be anything else than gettext-runtime and gettext-tools any more.
* gettext-tools/configure.ac (intl/Makefile): Update.
* NEWS: Mention that AM_GNU_GETTEXT_INTL_SUBDIR is gone.
