Add HDLC timeslot mode

This is useful for protocols that use HDLC framing for signalling on E1
timeslots, but which don't use LAPD inside (our E1INP_TS_TYPE_SIGN).

Examples are particularly a MTP2/MTP3 SS7 stack, like it is used on the
A interfaces or on the core network interfaces of classic
circuit-switched networks.

Change-Id: I2d75801df4d7cbb8dad325f4d6689841f0196fa6
4 files changed