Log Message:
trader: update to 7.18.

Version 7.18 (3rd August, 2022)
-------------------------------

Minor bug fix: remove the ``<icon>`` line from `trader.appdata.xml.in` so
that the icon is taken from the `trader.desktop` file instead, otherwise
Fedora builds fail with a message from ``appstream-util validate-relax``
that "tag-invalid: stock icon is not valid [trader.svg]".

Version 7.17 (3rd August, 2022)
-------------------------------

Fixed two TOCTOU (time-of-check / time-of-use) bugs that arose between
checking for the traditional data directory and creating a data directory
later.  Also fixed a bug when the ``HOME`` environment variable is empty:
use the current directory instead.

Updated the Brazilian Portuguese, Norwegian Bokmal, Swedish, French,
Esperanto, Serbian, German and English translations (in that order), with
thanks to Rafael Fontenelle, Johnny A. Solbu, Anders Jonsson, Frederic
Marchal, Felipe Castro, Miroslav Nikolih and Roland Illig respectively.

Updated the minimum version of GNU Autoconf required, giving the option
of compiling with C17 or C11 instead of C99.  Updated to the latest
snapshot of the Gnulib GNU Portability Library.