Add usage() fallback for saturnin www

src/libexec/saturnin-www

 # for more details
 #
 
+usage() {
+    usage_is "word..."      \
+             "-f file"      \
+             "-1|-2|-c|-C"
+}
+
 clipln() {
     #
     # Print primary clipboard and \n
     -2) src=xsec;          shift   ;;
     -c) src=xclp;          shift   ;;
     -C) src=xall;          shift   ;;
+    -*) usage                      ;;
     *)  break ;;
 esac done