gsmd should report error if can't connect to modem

[mickey@…]

If the modem doesn't respond to all the init commands within a certain
timeframe, gsmd should exit and not hang silently.

[laforge@…]

this has now been implemented.

In svn rev. 2131, gsmd has the following extensions:

1) at startup, we only fork into background (daemonize) after the GSM modem has

responded. We wait for 30 seconds and exit with error level otherwise.

2) every five minutes, we check if the modem is still alive. If we cannot

get any response at all (within 30 seconds), we terminate and write
a "FATAL" log line into the log file.