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/stdio.h

@@ -1,32 +0,0 @@
-#pragma once
-#include <stddef.h>
-#include <stdarg.h>
-
-typedef struct FILE FILE;
-
-extern FILE *stdin;
-extern FILE *stdout;
-extern FILE *stderr;
-
-#define EOF (-1)
-
-FILE  *fopen(const char *path, const char *mode);
-int    fclose(FILE *fp);
-size_t fread(void *ptr, size_t size, size_t nmemb, FILE *fp);
-size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *fp);
-int    fseek(FILE *fp, long offset, int whence);
-long   ftell(FILE *fp);
-int    fflush(FILE *fp);
-char  *fgets(char *s, int size, FILE *fp);
-int    fputs(const char *s, FILE *fp);
-int    feof(FILE *fp);
-int    ferror(FILE *fp);
-
-int    printf(const char *fmt, ...);
-int    fprintf(FILE *fp, const char *fmt, ...);
-int    sprintf(char *buf, const char *fmt, ...);
-int    snprintf(char *buf, size_t size, const char *fmt, ...);
-int    vsnprintf(char *buf, size_t size, const char *fmt, va_list ap);
-int    vfprintf(FILE *fp, const char *fmt, va_list ap);
-void write(int fd, const char* buf, unsigned long count);
-void exit(int code);