Use mremap on linux to grow map memory (broken)

[ysbaddaden]

Instead of mapping an absurd amount of memory, this patch attempts to only allocate the current size we need, and then call mremap to grow the memory.

Despite retaining the original address of the map (not the block aligned one), and making sure to align the map sizes to the kernel page size, mremap fails to grow the memory from the initial 4MB to 5MB.

refs #17