This way, host code can dynamically detect which interface supports
which functionality.
The related #defines should be moved to a header file that's shared with
the host application code.
Actually, at device level we want to specify 0, so we can select
individual Class/Subclass values at Interface values.
Table 9-8 of the USB2 Specification is quite clear about this.
When initializing the TC blocks, let's only configure the GPIO pins TCLK
and TIOB, and not the unused TIOA pin. That pin is actually used for
(separate) different functions in both qmod and owhw.
* we now actually route the EP0 control requests in DFU mode to the
correct handler (weak linker symbols are tricky)
* we now actually call code to read/write data from/to RAM/FLASH
This way we can easily check with 'diff' for differences in our code and
Atmel softpack. Also, this layout is more suitable for building various
different firmware images (e.g. factory-test, dfu-loader, main
application) for a variety of different boards (simtrace, owhw, qmod).
