build: Substitute archive version with configure
* gettext-tools/configure.ac (ARCHIVE_VERSION): New substituted
variable.
* gettext-tools/misc/gettextize.in (archive_version): New variable, set
to ARCHIVE_VERSION. Use it as the argument of AM_GNU_GETTEXT_VERSION.
* gettext-tools/tests/init-env.in (ARCHIVE_VERSION): New substituted
variable.
* gettext-tools/tests/autopoint-2: Use ARCHIVE_VERSION, instead of the
hard-coded version string.
* gettext-tools/tests/autopoint-3: Likewise.
