INT 2F - DBLSPACE.BIN - "GetDriveMapping" - GET DRIVE MAPPING
	AX = 4A11h
	BX = 0001h
	DL = drive number (0=A:)
Return: AX = status (see also #02804)
	    0000h successful
		if DL was compressed drive,
		    BL = host drive (bit 7 set if drive is compressed)
		else if DL was host drive,
		    BL = compressed drive
		else
		    BL = specified drive (if available for DoubleSpace)
		BH = DoubleSpace sequence number
	    other error code (0101h) (see #02804)
		apparently never returned for the MS-DOS 6.2 DoubleSpace
Note:	the compressed volume file for the specified compressed drive is
	  host:\DBLSPACE.sequence
SeeAlso: AX=4A11h/BX=0000h


(Table 02804)
Values for DBLSPACE function status:
 0000h	successful
 0100h	bad function
 0101h	invalid drive
 0102h	not a compressed drive
 0103h	drive already swapped
 0104h	drive not swapped
SeeAlso: #02806