Various fixes and improvements.

- fixed bug that caused IDLE to panic (irq hook inconsistency);
- kprintf() now accepts multiple arguments; moved to utility.c;
- prepare_shutdown() signals system processes with SIGKSTOP;
- phys_fill() renamed to phys_memset(), argument order changed;
- kmemset() removed in favor of phys_kmemset();
- kstrncpy() removed in favor of phys_copy();
- katoi, kstrncmp replaced by normal library procedure again;
- rm_irq_handler() interface changed (simply pass hook pointer);

kernel/proc.h

@@ -88,6 +88,7 @@ struct proc {
 #define END_PROC_ADDR (&proc[NR_TASKS + NR_PROCS])
 
 #define NIL_PROC          ((struct proc *) 0)		
+#define NIL_SYS_PROC      ((struct proc *) 1)		
 #define cproc_addr(n)     (&(proc + NR_TASKS)[(n)])
 #define proc_addr(n)      (pproc_addr + NR_TASKS)[(n)]
 #define proc_nr(p) 	  ((p)->p_nr)