build: Use a minimum gettext requirement rather than an exact one

In configure.ac, specify the minimum gettext version we require, rather than the exact one. This fixes a situation where the autoconf macros used for gettext will be the latest available on the system (for example, 0.20); but the copied-in Makefile.in.in will be for the exact version specified in configure.ac (in this case, 0.19).

In that situation, the gettext build rules will error out at make time with the message: *** error: gettext infrastructure mismatch: using a Makefile.in.in from gettext version 0.19 but the autoconf macros are from gettext version 0.20

Avoid that by specifying a minimum version dependency rather than an exact one. This should not cause problems as we haven’t committed any generated or external gettext files into git, so each developer will end up regenerating the build system for their system’s version of gettext, as expected.

See the subsection of https://www.gnu.org/software/gettext/manual/html_node/Version-Control-Issues.html for more information.

This patch is basically the same as https://gitlab.gnome.org/GNOME/geocode-glib/commit/6ba0e38fd1987be0de8432afd93b9a5c1f487b63

Signed-off-by: Fabiano Fidêncio fidencio@redhat.com