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/priv.h

@@ -61,7 +61,9 @@ struct priv {
 EXTERN struct priv priv[NR_SYS_PROCS];		/* system properties table */
 EXTERN struct priv *ppriv_addr[NR_SYS_PROCS];	/* direct slot pointers */
 
-/* Unprivileged user processes all share the same privilege structure. */
+/* Unprivileged user processes all share the same privilege structure.
+ * This id must be fixed because it is used to check send mask entries.
+ */
 #define USER_PRIV_ID	0
 
 /* Make sure the system can boot. The following sanity check verifies that