accept pub enum, and enums used as types

Implement pub support for enums, and also anonymous enums declared
in-place.

Also give the cdr of a `pub' form the form's own location, so a
error about what follows `pub' can say where it was written

tests/modules/greet-app.sex

@@ -21,4 +21,6 @@
   (printf "%d greetings\n" greet-count)
   (describe-fields greeting)
   (printf "\n")
+  (var m (enum mood) grumpy)
+  (printf "mood %d\n" m)
   (return 0))