[handover] first functional handover implementation

With this commit, we can successfully hand over a channel from one cell to
another cell.  We implement asynchronous intra-BSC (but inter-BTS) handover.

Changes:
* introduce new DHO log category
* extend rsl_chan_activate_lchan() with argument for HO reference
* introduce actual minimal handover decision making in handover_decision.c
* various fixes to bsc_handover_start() in  handover_logic.c
10 files changed
tree: d616821b44f212c8f7159cfd206bbc44ca41666b
  1. hlrsync/
  2. linux-kernel/
  3. openbsc/
  4. wireshark/