INT 62 u - FGDRIVER v3.03+ - "FG_BUTTON" - GET JOYSTICK BUTTON STATE
	AX = 0009h
	BX = joystick number (0001h or 0002h)
Return: AX = button states
	    bit 0: top button pressed
	    bit 1: bottom button pressed
Note:	the FGDRIVER functions are rearranged with each major release, but
	  their parameters do not change (see #03474)
SeeAlso: AX=0052h,AX=0056h,AX=005Eh,AX=0062h,AX=0077h