A variety of changes:

Reimplement "kernel_pmap" in the standard way.

Eliminate unused variables. (These are mostly variables that were
discarded by the machine-independent layer after FreeBSD 4.x.)

Properly handle a vm_page_alloc() failure in pmap_init().

Eliminate dead or legacy (FreeBSD 4.x) code.

Eliminate unnecessary page queues locking.

Eliminate some excess white space.

Correct the synchronization of pmap_page_exists_quick().

Tested by: gonzo