Add `kernel::process`. Update elf and mmu.

Use uints for pointers. Process stores physical address of the directory.
x86: improved cloning of page directory.
arm: Enable MMU
Avoid warnings (mostly imports and names)
sse2_dmem_movdqa_add
putx
exception putx
running
x86 mmu comments
Create x86_64 target
refactor lib.rs
CHECK? wrong update of x86 io mod
arm: uart backspace
x86: small fix: pub mod, dtreg
add arch common x86
common reg macros
fix some warnings
links in docs
gdbinits
syscalls
other work