mon_kpfret(): return from a kernel page fault

In the off chance the kernel faults and you want to try to recover, pass kpfret
the HW tf pointer.  It'll try to smp_idle, abandoning the kernel context.  This
means that any locks that were held are still locked, so you might deadlock.

This can't handle a nested fault (like if you fault while trying to run
kpfret).
Syscall debugging touchups

Syscall string saving was saving old strings, and the output of arguments was
imited to 32 bits.
82536: removes receive buffer pools

There weren't enough receive buffers.  If we get a large burst of traffic, all
of the NICs RBs could be pushed into the network stack (TCP conv rqs).  Then
we're unable to receive new packets.  If the app (kweb) doesn't read, we never
receive packets.  Kweb would have all of its threads blocked on a write, and
that write was unable to receive an ACK.

Instead of just increasing the number, or even growing the pool, I just opted
to remove the pools completely.  If we need/want NIC pools in the future, we
can add them back (preferably with a helper subsystem, so not all NICs reinvent
the wheel).