Deprecate hacks to support Gaudi v20 API
Somehow I never manage to get down to clean up LHCb code still relying on Gaudi v20 style API, so I'm not ready to integrate !597 yet.
This MR exposes with deprecation warnings the code that has to be adapted and is the first step to be able to merge !597 in %v40r0, in particular obsolete IInterface APIs and some obsolete header file.
Edited by Marco Clemencic