This patch doesn't really tests whether osmo-pcu can work on a multi-bts
environment, but it prepares the data structures to be able to do so at
any later point in time.
Change-Id: I6b10913f46c19d438c4e250a436a7446694b725a
There's no real point in using C++ there, and using C++ makes the
compiler fail to use llist_head in multi-bts patches added later due to:
"""
'offsetof' within non-standard-layout type is conditionally-supported
"""
Change-Id: I8965b5cc5a713e64788b5b6aa183d3035341ddbb