apr_pool_t with counter

Lack of tracking of the total size of all allocations made from a given apr_pool_t is a big pain for teeterl. I had to introduce yet another layer of indirection by adding xpool_t structure which is no more than a counter and apr_pool_t reference. Now most of the time the size of allocations are added up neatly to check when the threshold is reached and gc should kick in.
Recently I transgressed to the point of putting the size counting inside apr_pool_t thus producing a custom version of APR. Yes, it did make teeterl a bit smaller and cleaner and auxilliary allotments were counted better. On the other hand, the impure act of meddling with APR code made the installation of teeterl much longer and trickier. I still do not have a single person who managed to build and run teeterl on his/her machine and the recent change make the possibility even more remote. I am rolling everything back to xpool_t's.