INT 21 - DOS 3.2+ - IOCTL - SET LOGICAL DRIVE MAP

	AX = 440Fh
	BL = physical drive number (00h=default,01h=A:,etc))
Return: CF set on error
	    AX = error code (01h,0Fh) (see #01680 at AH=59h/BX=0000h)
	CF clear if successful
	    drive now responds to next logical drive number
Notes:	maps logical drives to physical drives, similar to DOS's treatment of
	  a single physical floppy drive as both A: and B:
	DR DOS 3.41-5.0 DRIVER.SYS does not support drive mapping and thus
	  always returns an error on this function
SeeAlso: AX=440Eh,INT 2F/AX=122Bh