[layer23] Implementation of signal loss criteria as defined in TS 05.08

[layer23] Implementation of signal loss criteria as defined in TS 05.08

There are two criterions for lossing a signal, idle mode and dedicated mode.
A counter counts down when a frame is dropped, and counts up when a valid
frame is received on  certain channel. The loss criterion is reached, if the
counter reaches 0. The values added to / removed from the counter and the
limits depend on the process.