Snippets for xscreensaver 6.17 from Fedora s390x

Sourced from https://kojipkgs.fedoraproject.org/packages/xscreensaver/6.17/1.fc46/data/logs/s390x/build.log.

../../driver/prefsw.c:1085:7: warning: variable ‘col’ set but not used [-Wunused-but-set-variable=]
 1085 |   int col = tab;
      |       ^~~

../../driver/xscreensaver-systemd.c:1421:9: warning: variable ‘retries’ set but not used [-Wunused-but-set-variable=]
 1421 |     int retries  = 0;
      |         ^~~~~~~

../../driver/demo-Gtk.c:5735:5: warning: assignment discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
 5735 |   s = strrchr (progname, '/');
      |     ^

/usr/include/ffmpeg/libavformat/avformat.h:1092:6: warning: ISO C99 doesn’t support unnamed structs/unions [-Wpedantic]
 1092 |     };
      |      ^

../../../hacks/glx/starwars.c:359:23: warning: variable ‘n’ set but not used [-Wunused-but-set-variable=]
  359 |                   int n = 0;
      |                       ^

../../../hacks/glx/fliptext.c:271:19: warning: variable ‘n’ set but not used [-Wunused-but-set-variable=]
  271 |               int n = 0;
      |                   ^

../../../hacks/glx/hydrostat.c:150:10: warning: variable ‘j’ set but not used [-Wunused-but-set-variable=]
  150 |   int i, j;
      |          ^

../../../hacks/glx/skulloop.c:226:7: warning: variable ‘i’ set but not used [-Wunused-but-set-variable=]
  226 |   int i;
      |       ^

../../../hacks/glx/highvoltage.c:641:7: warning: variable ‘i’ set but not used [-Wunused-but-set-variable=]
  641 |   int i;
      |       ^

../../driver/test-uid.c:204:3: warning: ignoring return value of ‘system’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
  204 |   system ("/bin/sh -c 'echo \"`whoami` / `groups`\"'");
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~