VIDCLOCK update notes:

v1.3, 08/15/90:
   Prioritized handling of the old clock vector.  Added a hook into the BIOS
   video handler to provide a steadier clock display.  Added dynamic shutdown
   during the use of graphics modes.  Memory requirement is up to 656 bytes.

v1.2, 11/28/89:
   Did some minor optimization of the installation routine.

v1.1, 09/11/88:
   Fixed a bug in the de-installation routine which caused some computers
   to lock up when VIDCLOCK removed itself from memory.  Reduced the
   memory requirements from 624 bytes to 608 bytes.  Increased the speed.
   Rewrote the time calculator to insure that seconds don't go to 60 (!).

v1.0, 08/21/88:
   Initial release.