ControlConfigGet gets the
configuration of a Control object (control) and
writes it into the structure pointed to by config, and
also writes it into the implementation-specific structure pointed
to by external (if external is not
NULL).
The configuration information in external is in
addition to the configuration information in config, i.e, the
configuration information in config and in external
is not the same information. Note that config or
external can be NULL (but not both NULL).