INT 31 - CauseWay v1.3 - "cwLoad" - LOAD ANOTHER CAUSEWAY PROGRAM AS OVERLAY

	AX = FF2Ah
	DS:EDX -> filename
Return: CF clear if successful
	    CX:EDX = CS:EIP of entry point
	    BX:EAX = initial SS:ESP for program
	    SI = PSP for overlay program
	CF set on error
	    AX = error code (01h file error, 02h not a 3P file, 03h no memory)
Note:	the returned PSP can be given to "RelMem" (AX=FF0Fh) to release the
	  overlay's memory and selectors; only selectors and memory allocated
	  during loading will be freed by RelMem unless one switches PSPs with
	  INT 21/AH=50h
SeeAlso: AX=FF00h,AX=FF24h