Put in infrastructure for the new send code.  The only code changes are in the
udsl_usb_probe and udsl_usb_disconnect functions, changed to initialize/finalize the
new fields (plus cleaned up a bit).  I couldn't resist a real code change while I was
there: freeing the memory used by the ATM after shutting it down, rather than before!
This doesn't make any difference since the shutdown routine doesn't work - so it still
oopses.  I will fix the shutdown routine later.