ASACORE-953 - Add About Client with Announce processing

ASACORE-953 - Add About Client with Announce processing and
              handler registration

              Enclose declaration of experimental calls with #ifdef
              ANNOUNCE_BASED_DISCOVERY ... #endif

Change-Id: I311b3244991c5dc7ea46172a6f4e2434cd1c7ba6
Signed-off-by: Eyal Ilsar <eyali@qce.qualcomm.com>
Merge "ASACORE-953 - Add About Client with Announce processing" into RB14.12