New phonet driver

[Daniele Forsi]

I recently added a new connection type that uses the cdc_phonet module
provided with the Linux kernel.
Feedback is welcome.
I tested it with a Nokia 5300 (Series 40 3rd) and a Nokia N73 (Series
60 3rd) and it should work also with later editions, possibly with
earlier editions too, but it doesn't add any new command so don't
expect any user visible change.

A typical configuration is:
connection=phonet
port=1
model=series40
See Docs/README-6510 for troubleshooting instructions.

If you were experiencing timeouts and disconnections with
connection=dku2libusb you can try if connection=phonet works better.

Pros:
* uses a module developed by Nokia, comes with Linux kernel
* doesn't need libusb
* doesn't need udev rules for unprivileged users

Cons:
* requires giving special capabilities to the executable if it is to
be used by unprivileged users, eg.
setcap cap_sys_admin,cap_net_raw=+ep $(which gnokii)
note that these capabilities are valid for the whole system, not only
for the phonet modules, so there's a potential security risk

-- 
Daniele Forsi