Things we have omitted for now:

- we don't make a deep copy of msg->lump_list; that means
  that all changes made prior to going stateful go lost
- we don't generate CANCELs for forked requests
- no ACK matching (waiting for To-tag)
- no SIP-wise HF comparison within T-matching
  (just memcmp)
- 6xx should be delayed indeed
- ACK of 2xx INV caching (avoid e2e retransmission
  of an ACK hit the proxy too)
- timers (408)

- Via:
	- branch
		- loop check
		- hash table & index
		- branch
	- mid & response routing

- T-language

To improve:
- too many memcpies
- faster syncing

Double-check: revire the T-state-machine