Compatibility: Win 3.x
Expects: AX    4004H
                                                                  
Returns: none
                                                                  
Info: After a previous call to INT 2fH 4003H (enter critical section),
you should use this fn to signal the end of the critical session.

If the VDD has been delaying an update to the video registers, it
will perform it immediately upon receipt of this call.

Calls to this fn without a preceding call to INT 2fH 4003H are
ignored by the VDD.

- -

INT 2fH 4004H: Exit Critical Section