Add new options for call waiting response in InCallUI

When an incoming call is received while there is already an active call,
the user will be given four choices for the response:

1) Left button: hold the current call and answer incoming call
2) Bottom button: end the current call and answer the incoming call
3) Right button: decline the incoming call
4) Top button: Send a text message to the incoming caller if texting
   is enabled

The framework changes include new hidden API for sending additional
information to Telecomm service, few constants, and a bug fix.

Change-Id: I642b330d856613fafc0526eb79dd97fedba4ce6a