no global 'interfaces' any more. Section name will be interface name.
- restructured module loading and init.
- dial string changed: parameters like 'b' no in number any more.
- send alert on alerting only (busy() and congestion() work now).
- better overlap sending (new parameter 'o' for dialstring to
send only the first two digits with CONNECT_REQ only, the remaining
digits and even digits following the dial() command, will be send
as INFO_REQ/Overlap).