Sort frontend names alphabetically

which is somehow better than "random" order.

include/pretty.sh

@@ -217,11 +217,11 @@ __echo() {
     esac done
     prettyfn=_pretty_$frontend
     case $frontend in
-        warn)     ;&
         debug)    ;&
         die)      ;&
+        think)    ;&
         usage_is) ;&
-        think)
+        warn)
             __echo_$src "$@" | $prettyfn >&2
             ;;
         *)