Use canonical names for globals

src/bin/saturnin.skel

 debug -v FFOO_PATH SATURNIN_LIBEXEC FFOO_CONFIG_PATH
 debug "\$@=$@"
 
-scmd=$1
+SATURNIN_SUBCOMMAND=$1
 shift
 
-case $scmd in
+case $SATURNIN_SUBCOMMAND in
     help)  print_help; exit $FFOO_EXIT_OK ;;
     *)
-        lexpath="$SATURNIN_LIBEXEC/saturnin-$scmd"
+        lexpath="$SATURNIN_LIBEXEC/saturnin-$SATURNIN_SUBCOMMAND"
         debug -v lexpath
         debug "\$@='$@'"
         test -x "$lexpath" && exec "$lexpath" "$@"
-        warn "invalid sub-command: $scmd"
+        warn "invalid sub-command: $SATURNIN_SUBCOMMAND"
         print_help; exit $FFOO_EXIT_USAGE
         ;;
 esac