INT 21 - DOS 2+ - IOCTL - GET INPUT STATUS

	AX = 4406h
	BX = file handle
Return: CF clear if successful
	    AL = input status
		00h not ready (device) or at EOF (file)
		FFh ready
	    AH may be destroyed (refer to note)
	CF set on error
	    AX = error code (01h,05h,06h,0Dh) (see #01680 at AH=59h/BX=0000h)
Notes:	files may not register as being at EOF if positioned there by AH=42h
	under DOS 5.0, on a successful return, AH contains either the next
	  character which will be read or 1Ah if at EOF; under a Windows95
	  DOS box, AH seems to be either unchanged or 00h
	this function was not supported by Digital Research's DOS Plus
BUG:	the CLOCK$ device under DR DOS 3.41 always indicates 'Ready'; this was
	  corrected in v5.0
SeeAlso: AX=4407h,INT 2F/AX=122Bh