fix package procedure object_id retrieval

In Oracle 12c (maybe 11g too but I haven't checked it) the object_id for a package procedure is not the same in all_procedures and all_objects. Without this fix the package spec was failing since `all_arguments` is based on the id of `*_all_procedures`.

Here is an example from a 12.1.0.2 environment:
``` sql
SQL> SELECT p.object_id p_obj_id, o.object_id o_obj_id
FROM all_procedures p, all_objects o
WHERE p.owner = 'SYS'
  AND p.object_name = 'UTL_ENCODE'
  AND p.procedure_name = 'BASE64_ENCODE'
  AND o.owner = p.owner
  AND o.object_name = p.object_name
  AND o.object_type = 'PACKAGE';

  P_OBJ_ID   O_OBJ_ID
---------- ----------
     11418	11416

1 row selected.
```