kernel - Correct second edge-case for machdep.pmap_mmu_optimize
* The pmap_release*() code was previously optimized to not invalidate
on pml4, pdp, pd, or pt pte's, only on terminal ptes. This invalidation
interferes with the PT replacement that the pmap_mmu_optimize feature
uses.
* The bug generally would only occur when memory is mmap()'d and munmap()'d
multiple times, which something like postgres will not do, but which
rtorrent and other programs will do.
* Correctly invalidate page tables (use invltlb) when PT pte's are replaced.
* Requires further testing. Default for this feature is still off.