o Replace KSTACK_PAGES with pages on panic() in pmap_new_thread(),
o Fix style bugs in adjacent code,
o Use NULL instead of 0 for pointers,
o Save the virtual kstack address if we create an alternate
kstack because 1) we can derive the physical (RR7) address
from it and 2) we need the virtual address for contigfree()
in pmap_dispose_thread(). Thus td_altkstack saves
td_md.md_kstackvirt.
02cda72148