the new AvailableApp

The new AvailableApp is working just great and sports a method, notFree, which can be used by Fork to catch that intermittent (and likely debugging-related) database corruption bug just a bit earlier.

One advantage of the new code is that it consolidates adjacent free blocks sooner. Another advantage is that you can check to see if a block has already been freed sooner and more easily.

On the down side, the validate utility is now broken and needs to be fixed. And the new code offers no help in the latest database corruption bug which occurs after a [b-tree] split, as that is a memory leak and can only be detected by the validate utility by walking through all structures.

(The sourceforge site is down as I write this, though the new code has been checked in.)