add MSDTC support

Yet another attempt, hoping all is well now. There are indeed some line endings issues.
I suggest adding ".gitattributes" to normailze line endings.
Because the whole Enlisting business is trigerred from the Open method on FbConnection.
Although this method sets the InnerConnection owner to itself it wont be visibile until the method is completed.
Thus a call to BeginTransaction without a direct reference to InnerConnection from the Open method would raise an exception.