INT 13,10 - Test for Drive Ready (XT & newer)

	AH = 10h
	DL = drive number (0=A:, 1=2nd floppy, 80h=drive 0, 81h=drive 1)

	on return:
	AH = status  (see INT 13,STATUS)
	CF = 0 if successful
	   = 1 if error

	- many good programming references indicate this function is only
	  available on the AT, PS/2 and later systems, but all hard disk
	  systems since the XT have this function available