INT 21 - DOS 3.2+ - IOCTL - GENERIC BLOCK DEVICE REQUEST

	AX = 440Dh
	BL = drive number (00h=default,01h=A:,etc)
	CH = category code (see #01558)
	CL = minor code (function) (see #01559)
	DS:DX -> (DOS) parameter block (see #01560,#01562,#01563,#01564,#01565)
	SI:DI -> (OS/2 comp box) parameter block (see #01566,#01568,#01569,#01572)
Return: CF set on error
	    AX = error code (01h,02h,etc.) (see #01680 at AH=59h/BX=0000h)
	CF clear if successful
	    DS:DX -> data block if CL=60h or CL=61h
Notes:	DOS 4.01 seems to ignore the high byte of the number of directory
	  entries in the BPB for diskettes.
	functions 46h and 66h undocumented in DOS 4.x, documented for DOS 5+
	the DUBLDISK.SYS v2.6 driver only supports minor codes 60h and 67h
	DR DOS 3.41-6.0 only support minor codes 40h-42h and 60h-62h; all
	  other minor codes return error code 16h
	some PCMCIA calls reportedly appear to be dangerous for MS-DOS versions
	  prior to 5.0
	minor code 60h normally produces no I/O except with AutoMount=1 for
	  DBLSPACE/DRVSPACE
SeeAlso: AX=440Ch,AX=440Dh/CX=084Ah,AX=440Dh/CX=0871h,AH=69h,INT 2F/AX=0802h
SeeAlso: INT 2F/AX=122Bh