- Fixed comments in various system call handlers. Work in progress on new

sys_privctl() call to dynamically start servers and drivers.

- Shutdown sequence slightly adjusted: called as watchdog timer to let the
  busy sys_abort() call from the PM return first.

- Changed umap_bios() to have more restrictive check: BIOS memory is now
  allowed in BIOS_MEM_BEGIN to END (interrupt vectors) and BASE_MEM_TOP
  to UPPER_MEM_END. Hopefully this keeps QEMU and Bochs happy.

kernel/system/do_devio.c

@@ -22,7 +22,7 @@
 PUBLIC int do_devio(m_ptr)
 register message *m_ptr;	/* pointer to request message */
 {
-    /* Perform actual device I/O for byte, word, and long values. */
+/* Process a single I/O request for byte, word, and long values. */
     if (m_ptr->DIO_REQUEST == DIO_INPUT) { 
       switch (m_ptr->DIO_TYPE) {
         case DIO_BYTE: m_ptr->DIO_VALUE = inb(m_ptr->DIO_PORT); break;