Convert postgresql driver ReflectionBase manual XInterface
implementation to use ::cppu::WeakComponentImplHelper.

Change-Id: I738bd7df33de9c0fe0e3242eb5a4fab6a8dcb3f0
Reviewed-on: https://gerrit.libreoffice.org/18207Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>