generic builtin functions

I am looking at creating a few generic functions builtin for the enum 
stuff. These would be tied to each enum type as it is created. However, 
they should not really appear in pg_proc initially, as there wouldn't be 
any enum types to tie them to anyway. But I want them to have reserved 
oids and appear in the list of builtins.

So I could hack genbki to exclude them, or I could add some code to 
remove them from pg_proc after the event. Bioth of these some a bit 
hackish. Maybe there's a trick I'm not aware of?

cheers

andrew