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/include/strings.h

@@ -1,8 +0,0 @@
-#pragma once
-#include <stddef.h>
-
-int    strcasecmp(const char *s1, const char *s2);
-int    strncasecmp(const char *s1, const char *s2, size_t n);
-void   bzero(void *s, size_t n);
-void   bcopy(const void *src, void *dest, size_t n);
-int    bcmp(const void *s1, const void *s2, size_t n);