Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

$Id$ -> $FreeBSD$

o Add the -foreground switch. This switch behaves like -background except
that ppp stays in the foreground.
o Add the -quiet switch to quieten ppps startup
o Add the -nat flag and discourage the use of the -alias flag. Both do
the same thing.
o Correct some nat usage strings.
o Change the internal ``alias'' command to ``nat''.

o Redesign the layering mechanism and make the aliasing code part of
the layering.

We now ``stack'' layers as soon as we open the device (when we figure
out what we're dealing with). A static set of `dispatch' routines are
also declared for dealing with incoming packets after they've been
`pulled' up through the stacked layers.

Physical devices are now assigned handlers based on the device type
when they're opened. For the moment there are three device types;
ttys, execs and tcps.

o Increment version number to 2.2
o Make an entry in [uw]tmp for non-tty -direct invocations (after
pap/chap authentication).
o Make throughput counters quad_t's
o Account for the absolute number of mbuf malloc()s and free()s in
``show mem''.
o ``show modem'' becomes ``show physical''.