Enable --help (friendly usage()) in saturnin__conf()

src/shellfu/saturnin.sh

         -P:*)   ig_mode=$1; ig_query=""; shift 1; break ;;
         .*:*)   warn "bad syntax: $*"; _saturnin__conf_usage ;;
         *.*:*)  ig_mode=-e; ig_query=$1; shift 1; break ;;
+        --help:*) _saturnin__conf_usage -e 0                 ;;
         *)      warn "bad syntax: $*"; _saturnin__conf_usage ;;
     esac done
     test -n "$ig_mode" || { warn "could not determine inigrep mode"; _saturnin__conf_usage; }
     # Show usage message and exit
     #
     PRETTY_USAGE="self=${0##*/} conf" \
-    mkusage "[options] [-e] SECTION.KEY [FNAME]"                               \
+    mkusage "$@"                                                               \
+            "[options] [-e] SECTION.KEY [FNAME]"                               \
             "[options] -r SECTION.KEY [FNAME]"                                 \
             "[options] -K SECTION [FNAME]"                                     \
             "[options] -P FNAME"                                               \