Instead of having a single mmap(2)'ed file inside which we allocate
the necessary chunks, put each chunk in its own file and use two index
files (MGR/CHILD) to keep track of them.

Major benefits:

* You don't need to guess how much VSM space you need at startup.

* VSM chunk Identifier (and therefore VSC counter names) are unlimited length.

Minor benefits:

* VSM API has simpler and explainable semantics now.

* The bogo-you-didnt-guess-right-malloc-VSM allocations are gone.

* -t argument moves up/down to VSM level and works the same through-out.

* VSM/VUT utils now stay attached even if the MGT process restarts.

Some relatively minor adjustments are still to come before the VSM API is frozen
and the .map file finalized for the release.