It appears that some expensive USB sound cards do not like the DFU interface
being claimed at the same time the kernel starts using a different endpoint.
I suspect this is a device bug or limitation in some reference implementation
somewhere, but seeing as we only need the interface when verifying or writing
new firmware the sensible thing to do is not claim it until required.
Fixes: https://github.com/hughsie/fwupd/issues/50
The DFU specification specifies that only one of the DFU interfaces has to
export a functional descriptor; I assumed they all had to. Adding support
for this kind of device rapidly turned into a massive restructure and it was
all too complicated anyway.
Reorganise the code so that we can support these kinds of devices and clean up
the API so it's sane and easy to use. This also allows us to generate the
GObject introspection GIR and to also install libdfu as a shared library.
If you've got any comments about the API, please shout now as when 6.0 is
released it will become API and ABI stable.
