This makes it possible to use the pkexec tool to execute u-a from GUI
programs.

We need to bump the gettext build-dependency to at least 0.19.7 which is
the first version introducing ITS support and GETTEXTDATADIR variable
support (GETTEXTDATADIRS support was added in 0.19.8).

Proposed-by: Boyuan Yang <073plan@gmail.com>