Revert HZ to 100 what it was

Rework NetBSD/usermode pmap fixing some oddities that were left over from
earlier times when we were forced to run PIE executables and were forced to
use a KVM above the kernel.

get rid of urkelvisor, and use same MD majors as the host

Update kmempages; how does this relate to kvmspace though?

Compile in syscall name table so urkel debugging code can print out the names
of the system calls so its more clear where it strands.`

Add usermode kernel supervisor, can be disabled with 'no options URKELVISOR'

Bump NKMEMPAGES from 512 to 2048 for NetBSD/usermode. This will be sufficient
for a 128 MB amd64 machine. Might better be parameterized one day.

Move NKMEMPAGES from GENERIC to std.usermode and clarify the meaning of
MEMSIZE in the GENERIC kernel.

define opt constants away for i386

*** empty log message ***

Import work-in-progress NetBSD/usermode port.