Use pmap_TLB_invalidate instead of invltlb_1pg to eliminate
unnecessary IPIs.
pmap_remove, pmap_protect and pmap_remove_pages:
Use pmap_TLB_invalidate_all instead of invltlb to eliminate
unnecessary IPIs.
pmap_copy:
Use cpu_invltlb instead of invltlb when updating APTDpde.
pmap_changebit:
Rather than deleting the unused "set bit" option (which may be
useful later), make pmap_changebit an inline that is used
by the new pmap_clearbit procedure.
Collectively, the first three changes reduce the number of TLB shootdown
IPIs by 1/3 for a kernel compile.