INT 21 - MS-DOS 7.0+ - GENERIC IOCTL - LOCK LOGICAL VOLUME

	AX = 440Dh
	CX = 084Ah / 484Ah
	    (category code 08h for FAT12/16, 48h for FAT32; minor code 4Ah)
	BL = drive number (01h=A:,02h=B:,etc)
	BH = lock level (00h-04h)
	DX = drive permissions (see #01575) for Level 1 lock or second
	    Level 0 lock when formatting
Return: CF set on error
	    AX = error code (01h,02h,etc.) (see #01680 at AH=59h/BX=0000h)
	CF clear if successful
Notes:	the logical volume must be locked before direct disk accesses are
	  permitted by Windows95/98
	the commandline LOCK issues a level 4 lock
	Windows98 only permits lock levels 0 and 4
BUG:	Windows98 will return an error (invalid function) if the specified
	  drive number is zero or more than 32, but only allocated 26 bytes
	  for recording locks, so BL=1Bh..20h will trash internal data
	  structures
SeeAlso: AX=440Dh"DOS 3.2+",AX=440Dh/CX=084Bh,AX=440Dh/CX=086Ah
SeeAlso: AX=440Dh/CX=086Ch