. added rm_irq_handler which un-links an irq handler from the linked

list of handlers, callable by irqctl system call
 . workaround for hanging keyboard bug after shutdown.. if key is pressed
   during or after shutdown procedure, keyboard stops working. It looks like
   irq 1 gets stuck high if no keyboard reading is done (e.g. because the
   irq is masked or tty driver has exited). Workaround is to leave irqs
   enabled until the last second, and call shutdown() immediately after the
   last driver has stopped (tty task). This way the chance of an unserviced
   interrupt occuring is negligible.

kernel/system.c

@@ -236,7 +236,7 @@ int proc_nr;				/* slot of process to clean up */
 PUBLIC int generic_handler(hook)
 irq_hook_t *hook;	
 {
-/* This function handles hardware interrupt in a simpel and generic way. All
+/* This function handles hardware interrupt in a simple and generic way. All
  * interrupts are transformed into messages to a driver. The IRQ line will be
  * reenabled if the policy says so.
  */