autopoint: Respect AM_GNU_GETTEXT_REQUIRE_VERSION
* gettext-runtime/m4/gettext.m4 (AM_GNU_GETTEXT_REQUIRE_VERSION): New macro.
Bump serial to 67.
* gettext-tools/doc/autopoint.texi: Mention AM_GNU_GETTEXT_REQUIRE_VERSION.
* gettext-tools/misc/gettextize.in: Check if AM_GNU_GETTEXT_VERSION is
used.
* gettext-tools/misc/autopoint.in: Respect AM_GNU_GETTEXT_REQUIRE_VERSION.
* gettext-tools/tests/autopoint-2: Check AM_GNU_GETTEXT_REQUIRE_VERSION.
