Move the T_defs API to libosmocore as osmo_tdefs: remove the local T_defs API
and use libosmocore's osmo_tdef* API instead.
The root reason is moving the mgw_endpoint_fsm to libosmo-mgcp-client to be
able to use it in osmo-msc for inter-MSC handover.
When adding osmo_tdef, the new concept of timer groups was added to the API. It
would make sense to apply group names here as well, but do not modify the VTY
configuration for timers. The future might bring separate groups (or not).
Depends: Ibd6b1ed7f1bd6e1f2e0fde53352055a4468f23e5 (libosmocore)
Change-Id: I66674a5d8403d820038762888c846bae10ceac58
a6078fe1d8