PPP generic layer update

[Michal Ostrowski <mostrows@xxxxxxxxxxxxxxxxx>]

These changes look good .... I get the impression that this may just
solve a problem that me and Jamal found yesterday.  We would like to
be able to kill a channel from within the kernel when we recognize a
PPPoE disconnect.  With this patch it appears to me that we can do
this by unregistering the channel and pppd will be notified of this
via /dev/ppp and subsequently close the tty_fd.  Is this correct?

I'll take this opportunity to mention that I've successfully ported my 
old pppd hack to use Mitch's pppd patch and it all seems to work quite 
well.  Jamal is currently in the process of incorporating his
discovery code into a pppd plugin and so we'll be able to present a
PPPoE solution for comments shortly.

Michal Ostrowski
mostrows@xxxxxxxxxxxxxxxxx