INT 67,5D - Enable/Disable OS Functions (LIM EMS 4.0+)

	AH = 5D
	AL = 00  enable OS function Set
	     01  disable OS function Set
	     02  return access key
	BX,CX = access key returned by first invocation


	on return:
	AH = status  (see EMS STATUS)
	BX,CX = access key, returned only on first invocation of function


	- function 2 resets memory manager, returns access key at next
	  invocation