Use the history API instead of hard-coded calls to dbz stuff

[Julien-Elie]

Some history related things are hard-coded into INN, avoiding the history API:
For example in innd/innd.c:

    i = dbzneedfilecount();
    if (!fdreserve(
            3 + i)) { /* TEMPORARYOPEN, history stats, INND_HISTORY and i */

Such functions should not be called when not using the hisv6 storage backend.

makedbz and such things are called during expire without asking the history API. All dbz-related things should be moved into the history/hisv6 source directory and should be started via the history API, or should at least check if hismethod is hisv6.