For the BSC we will have the gsm48_hdr and don't need to
find data within SCCP. For legacy reasons we need to
initialize con_type, imsi, reject causes early on and
need to do the same in the filter method.
This means we need to require a talloc context and
simply operate on the list. I had considered creating
a structure to hold the list head but I didn't find
any other members so omitted it for now.
Move the filter methods to the filter module. This is
still only usable for the NAT and the _dt/_cr filter
routines need to move back to the bsc_nat in the long
run.
Holger Hans Peter Freyther