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.

user/libxunil/Cargo.toml

@@ -10,3 +10,9 @@ crate-type = ["staticlib"]
 [profile.release]
 panic = "abort"
 opt-level = "s"
+
+[target.'cfg(target_arch = "x86_64")'.dependencies]
+x86_64 = "0.15.4"
+
+[profile.dev]
+panic = "abort"