add a function to call pmap_growkernel if necessary.  will be used by vmem.
add pool_cache_bootstrap_destroy.  will be used by vmem.
add flags for vmem_create to mark some arenas for bootstrap.
pmap_get_physpage: don't bother to associate kernel ptps to uvm objects.
make pmap_growkernel interrupt-safe.
- separate kernel va allocation (kernel_va_arena) from
  in-kernel fault handling (kernel_map).
- add vmem bootstrap code.  vmem doesn't rely on malloc anymore.
- make kmem_alloc interrupt-safe.
- kill kmem_map.  make malloc a wrapper of kmem_alloc.
uvm_map_checkprot: a kludge for mem(4).
sync with head.
sync with head.
sync with head.
sync with head.