Generic AC Source Fix, plus New DC Disconnect SPN

Proposed by Martin Perlot, SilverLeaf Electronics.

1) Change the DSA for the Generic AC Source from 139 to 140.

2) Add to DC Disconnect (DSA 139), SPN 256: Solenoid Failure

Edit (1) is required because the DSA 139 is already implemented as the DC Disconnect. Fortunately, there are no products known on the market that currently implement the Generic AC Source DSA.

To clarify: the DC Disconnect

To clarify: the DC Disconnect SPN, this should be coded as MSB=1, ISB=Instance, and LSbits as 0.