Fix MSVC warnings, win64 bug

- Use qSort and function pointer instead of struct operators and std::sort
  to appease MSVC.

- Simplify DFInstanceWindows::map_virtual_memory loop

- Store real base address offset instead of reading 0x400000 from PE
  header.
I think it would be fine to remove them. It's intended as a dev-tool more than anything else, and the df-structure tools are much more useful.