2) Killed i386pagesperpage as it is not used by anything.
3) Fixed benign miscalculations in pmap_bootstrap().
4) Moved allocation of ISA DMA memory to machdep.c.
5) Removed bogus vm_map_find()'s in pmap_init() - the entire range was
already allocated kmem_init().
6) Added some comments.
virual_avail is still miscalculated NKPT*NBPG too large, but in order to
fix this properly requires moving the variable initialization into locore.s.
Some other day.