Update mkdemo with newer shellfu

dotfiles.config/Xlib/colorscheme/mkdemo

@@ -48,7 +48,7 @@ css() {
     echos "}"
 }
 
-test -n "$CSDEMO_FNAME" || usage_is "scheme.Xresources"
+test -n "$CSDEMO_FNAME" || mkusage "scheme.Xresources"
 
 htmlhead                 >  "$CSDEMO_FNAME.html"
 <"$CSDEMO_FNAME" xd2html >> "$CSDEMO_FNAME.html"