Revert "POOL_DEBUG is commented out of GENERIC as of OpenBSD 5.5"

This reverts commit 57dda2ed2ff1389259342105717cb4871ef9aab3.
Revert "Clarifiy a preferred divisibility by 64 for cylinder count."

This reverts commit 0024eb0414ac459579daf0781690ee80ac37852e.