 - Add pmap locking to ia64's pmap_enter() and pmap_enter_quick().  (This    brings ia64 to parity with alpha, amd64, and i386 in this area.)  - Prevent a race in pmap_find_pte(): If pmap_find_pte() sleeps in    uma_zalloc(), another thread could allocate a pte at the same address.    Instead, sleep at a higher level and retry the lookup before retrying    the allocation.
 - Add pmap locking to ia64's pmap_enter() and pmap_enter_quick().  (This
   brings ia64 to parity with alpha, amd64, and i386 in this area.)
 - Prevent a race in pmap_find_pte(): If pmap_find_pte() sleeps in
   uma_zalloc(), another thread could allocate a pte at the same address.
   Instead, sleep at a higher level and retry the lookup before retrying
   the allocation.

Reviewed and tested by:	marcel@

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