gettextize: Fix bad interactions between autoreconf and autopoint.

gettextize: Fix bad interactions between autoreconf and autopoint.

Reported by Sebastian Pipping <sebastian@pipping.org>
in <https://savannah.gnu.org/bugs/index.php?66968>.

* gettext-tools/m4/Makefile.am (aclocaldir): Remove variable.
(pkgdatadir, macrosdir): Add variables.
(macros_DATA): Renamed from aclocal_DATA.
(install-data-local, uninstall-local, uninstall-macros): New targets.
* gettext-tools/misc/gettextize.in: Copy the *.m4 files from
$datadir/gettext/m4, not from $datadir/aclocal.
* gettext-tools/doc/gettext.texi (aclocal): Don't recommend to add option
--install to ACLOCAL_MFLAGS. Instead, recommend one-time use of --system-acdir.
* PACKAGING: Expect *.m4 files in $prefix/share/gettext/m4, not in
$prefix/share/aclocal.
* NEWS: Mention the fix.