Fix for the onPageTables formula

 - relies on HierarchyThreshold to find a good place to start the
   cleanup
 - validity of the formula was tested for ALL pagesizes ranging from 16
   byte to 32 Mbyte with ALL possible chunkSizes that result in a
   hierarchical page layout for the given pagesize.
 - the previous comment mentioned, that it might be possible to free
   only those areas that were used as metadata based on the previous
   chunkSize. This does NOT work: if the new metadata includes some
   parts that were previously used as payload-data, this parts will
   still be non-zero and the bug will occur again.
 - closes #70
Merge pull request #71 from slizzered/issue70-fix_for_mallocMC

Fix for the onPageTables formula