Make some adjustments to low level madvise/mcontrol/mmap support code to

Make some adjustments to low level madvise/mcontrol/mmap support code to
accomodate vmspace_*() calls.

Reformulate the new vmspace_*() calls so they operate similarly to the
MAP_VPAGETABLE and mcontrol() calls.  This also makes vmspace's more
'programmable' in the sense that it will be possible to mix virtual
pagetable mmap()ings with other mmap()ing in a vmspace.

Fill in the code for all the new vmspace_*() calls except for
vmspace_ctl().  NOTE: vmspace calls are effectively disabled unless
vm.vkernel_enable is turned on, just like MAP_VPAGETABLE.

Renumber the new mcontrol() and vmspace_*() calls and regenerate.