)
Call NESL function DeRegisterEventProducer with:
	BX = 0002h
	ES:SI -> PECB previously passed to RegisterEventProducer (see #03021)
Return: AX = completion code (0000h, 8002h, 8008h) (see #03019)
	ES:SI -> still points to PECB
	BP,DS,STACK preserved
Desc:	Allows a module to de-register as a producer of a given event class
SeeAlso: #03014,#03018