INT 49 - TI Professional PCIBM PC - CRT - GET START-OF-DISPLAY POINTER
	AH = 17h
Return: DX = current offset at which display starts
Note:	AH=00h,04h,05h,0Bh,0Ch,0Dh,0Fh are documented as NOPs
SeeAlso: AH=01h,AH=02h,INT 10/AH=FEh