Compatibility: 6.0+
Expects: AX    4a11H (mux number)
BX    0002H (DoubleSpace fn code)
DL    compressed drive number to swap with its host
Returns: AX    DoubleSpace API Error Code (0000H=success)
Info: This swaps a DoubleSpace compressed drive's ID with the ID of its
host drive.

For instance, if drive C contains a CVF  named DBLSPACE.000, then
when DoubleSpace starts up, it will mount that CVF as drive J
(for example).

To set up so the compressed volume is drive C (and set the host
as drive J), you would set DL to 9 (0=A, 1=B,...9=J)

Notes:   There is no "unswap" variation of this fn; if you attempt to
swap a previously-swapped drive, this fn returns an error.

  DBLSPACE.BIN performs disk swapping automatically, based on
settings in DBLSPACE.INI.  I recommend against using this fn.

- -

INT 2fH 4a11H BX=0002H: Dblspace Swap Drive