Feature #3618: Inter-MSC hand-over support
GSUP protocol extension for inter-MSC HO
Inter-MSC hand-over traditionally requires signalling on the MAP based "E" interface between MSCs. As OsmoMSC doesn't have MAP, we have to add the related bits to GSUP.
This includes the questions on how to represent the equivalent to the persistent TCAP dialogue that exists throughout a call in MAP. It also includes the question on how to identify the target MSC, and how to route the message to a given destination MSC (via OsmoHLR as GSUP router).