INT 62 u - FGDRIVER v4.02 - "FG_GETBLOCK" - GRAB RECTANGLE OF DISPLAY
	AX = 003Ch
	ES:BX -> buffer for screen contents
	CX = leftmost column
	DX = rightmost column
	SI = top row
	DI = bottom row
Notes:	the FGDRIVER functions are rearranged with each major release, but
	  their parameters do not change (see #03474 at AX=0000h)
	In text modes, coordinates are character positions; in graphics modes,
	  they are defined in screen space, and the left and right edges are
	  adjusted to a byte boundary if necessary
	Use "FG_IMAGESIZ" (see AX=005Ch) to determine the required buffer size
SeeAlso: AX=0044h,AX=005Ch,AX=0098h