Make sure that zero pages get swapped out properly.
Make sure that zero pages get swapped out properly.

This isn't quite as efficient as it could be, but ideally nothing should
ever swap.

rvedam/Mezzano,AugustusHuang/Mezzano,varjagg/Mezzano,rvedam/Mezzano,varjagg/Mezzano,AugustusHuang/Mezzano,froggey/Mezzano,froggey/Mezzano