Bugfix.

    Squandering the allocated size in pool segment
     - New pool segments are needed when existing ones are full
     - In this case, the requested size was squandered in the start of the pool segment
     - This was never a problem, with allocates below half the pool segment size
     - AxeSMTP allocates larger blocks and ran into problems as a first
     - Squandered memory in the beginning, remainder sticks out of the pool segment