Check if kernel calls is allowed (from process' call mask) added. Not yet

enforced. If a call is denied, this will be kprinted. Please report any such
errors, so that I can adjust the mask before returning errors instead of
warnings.

Wrote CMOS driver. All CMOS code from FS has been removed. Currently the
driver only supports get time calls. Set time is left out as an exercise
for the book readers ... startup scripts were updated because the CMOS driver
is needed early on. (IS got same treatment.) Don't forget to run MAKEDEV cmos
in /dev/, otherwise the driver cannot be loaded.

kernel/priv.h

@@ -21,9 +21,10 @@ struct priv {
   sys_id_t s_id;		/* index of this system structure */
   short s_flags;		/* PREEMTIBLE, BILLABLE, etc. */
 
-  short s_call_mask;		/* allowed system call traps */
-  sys_map_t s_send_mask;	/* allowed send destinations */
-  long s_sys_mask;		/* allowed kernel calls */
+  short s_trap_mask;		/* allowed system call traps */
+  sys_map_t s_ipc_from;		/* allowed callers to receive from */
+  sys_map_t s_ipc_to;		/* allowed destination processes */
+  long s_call_mask;		/* allowed kernel calls */
 
   sys_map_t s_notify_pending;  	/* bit map with pending notifications */
   irq_id_t s_int_pending;	/* pending hardware interrupts */