INT 62 u - FGDRIVER v4.02 - "FG_GETXBOX" - GET WIDTH OF VERTICAL BOX LINES
	AX = 0051h
Return: AX = width (in pixels) of left and right edges of rectangles
Note:	the FGDRIVER functions are rearranged with each major release, but
	  their parameters do not change (see #03474 at AX=0000h)
SeeAlso: AX=0006h,AX=0007h,AX=0008h,AX=006Bh