The NOTICE messages about truncating the function name are harmless and they can be ignored. Postgresql onely uses the first 32 characters of an identifier, and it ignores the rest, but as long as the first 32 characters are unique, you won't have any problems.
As far as the parsing error, I'm not sure about that. I'm able to call content_type__register_child_type without any errors. Could you do the following and post the results:
select definition from acs_func_defs where fname = 'content_type__register_child_type';
