Leaner ArrayAllocator and BitMaps

The ArrayAllocator class is used to use mmap, instead of malloc, for large array allocations. The current implementation uses state variables to remember what type of allocation was used. This is unnecessary, and by making ArrayAllocators AllStatic I can reduce the size of other classes that use ArrayAllocators.

One important user of ArrayAllocators are BitMaps, and by doing this change we open of for the possibility to use smaller BitMaps.