Fix negative numbers
Add an mmap_entry_t structure
Add screen_put_uint
Paging working + Debugging symbols

PMM reworked (need to document major changes)
VMM reworked
Can now identity-map critical regions that GRUB gives us
Rename some things in multiboot.h to make them easier to understand and
closer to the real GRUB specification
Fix documentation

FIXME: We still need to move the PMM to some better place. Right now it
identity-maps to 0xD0000000, which is huge and may not exist in loads
of systems.