information schema/aclexplode doesn't know about default privileges

Try this:
   create function foo(int) returns int as $$ select $1 $$ language sql;
   select * from information_schema.routine_privileges;

This ought to show EXECUTE privilege on the new function, but it
doesn't, because proacl is null, and nothing in the information schema
handles that specially.

I've pondered some ways to fix that.  One would be to add a variant of
aclexplode() that takes a parameter telling which catalog the acl datum
came from, and aclexplode() could then substitute the data received
acldefault() for null values.  The other way would be to handle this
entirely in the information schema SQL (either using some coalesce calls
or perhaps a UNION).  But that would mean duplicating the knowledge of
acldefault() in a second remote place.  So I'm thinking that handling it
in aclexplode() would be better.

Comments?