Add a scheduler which just keeps of processes for now, and a

with_process to interact with them. User space now has it's own address
space and mapper which means we will be able to allocate memory for it.
I added a bunch of functions as stubs into libxunil which are required
for doomgeneric.

kernel/src/main.rs

@@ -13,6 +13,8 @@ use limine::request::{
 };
 pub mod arch;
 pub mod driver;
+pub mod mm;
+pub mod task;
 pub mod userspace_stub;
 pub mod util;