configure: Relax gettext requirement
Since commit 3a2dd305, we've added gettext 0.19.8 as a dependency for libosinfo. However, it broke libosinfo build on Ubuntu 16.04 as the gettext provided by them is 0.19.7.
Taking a look at the "noteworthy"* changes, seems that for our usecase we can just depend 0.19.7 and keep building on Ubuntu 16.04
*: https://lists.gnu.org/archive/html/info-gnu/2016-06/msg00003.html
Signed-off-by: Fabiano Fidêncio fidencio@redhat.com