Increase UIDs to 96 bits w/ C/F prefix - BIT-1016

- The bit-length is adjustable via redef'ing bits_per_uid.

- Prefix 'C' is used for connection UIDS (including IP tunnels) and
  'F' for files.
Merge branch 'master' into topic/jsiwek/uid
Fix UID compiler warning/error & missed baselines.
Merge remote-tracking branch 'origin/topic/jsiwek/uid'

* origin/topic/jsiwek/uid:
  Fix UID compiler warning/error & missed baselines.
  Increase UIDs to 96 bits w/ C/F prefix - BIT-1016