Users of umodem (the USB modem driver), please take note!

I've changed the umodem driver by splitting into two parts: umodem and ucom.
The config file now has to look like this:
umodem* at uhub?
ucom* at umodem?

The reason for this split is that the code that makes up ucom can now be reused
for other drivers, e.g. serial ports, and all the devices will show up as /dev/ttyU?.

Please report any problems as usual.

--

        -- Lennart