plan cache doesn't clean plans with references to dropped procedures

Hi

I am playing with fixing the speed of CALL statement in a non atomic
context, and when I tested my patch I found another issue of CALL statement
- an invalidation of plans doesn't work for CALL statement (in atomic
context).

CREATE OR REPLACE FUNCTION public.fx(a integer)
RETURNS integer
LANGUAGE plpgsql
AS $function$
begin
return a;
end;
$function$

create or replace function fxo(a int)
returns int as $$
begin
return fx(a);
end;
$$ language plpgsql;

drop function fx;

-- create fx again
create or replace function fx(a int)
returns int as $$
begin
return a;
end;
$$ language plpgsql;

-- should be ok
select fxo(10);

-- but
create procedure pe(a int)
as $$
begin
end;
$$ language plpgsql;

create or replace function fxo(a int)
returns int as $$
begin
call pe(a);
return fx(a);
end;
$$ language plpgsql;

-- ok
select fxo(10);

postgres=# drop procedure pe;
DROP PROCEDURE
postgres=# create procedure pe(a int)
as $$
begin
end;
$$ language plpgsql;
CREATE PROCEDURE
postgres=# select fxo(10);
ERROR: cache lookup failed for function 16389
CONTEXT: SQL statement "CALL pe(a)"
PL/pgSQL function fxo(integer) line 2 at CALL

Regards

Pavel