I think in this package
there is a DFU class device library, dated November 2015.
I don't know how complete it is.EDIT
I also found here
FS device lib 4.0.0 which is the closest to the bootloader core files. I did a quick compare, beside typedefs there are minor changes, which I don't know how they can influence the functionality.
And, btw, they still don't have the little endian stuff in their code, dated January 2013.