[Arm-netbook] stm32f072 usb firmware

[Luke Kenneth Casson Leighton]

hi peter, et al,

i managed to find a variant of libopencm3 which has usb support for
the stm32f072, i compiled the cdcacm example and it worked.  i will
write up some notes later but here's a start:

https://github.com/kuldeepdhaka/libopencm3/tree/usb-rewrite
https://github.com/kuldeepdhaka/libopencm3-examples/tree/usb-rewrite
http://hands.com/~lkcl/usb_req_done.patch

peter i sent phil the ssh key, please do consider joining the mailing
list so that things can be coordinated without cc.

the above branch is... well... it's literally one of the first times
that libopencm3 has run usb code on an stm32f072 nucleo board.  it
means that certain things aren't going to be there.  with two of us,
peter, doing testing and development, the libopencm3 team on
irc.freenode.net will have the encouragement they need to move things
forward: we are, however, going to have to help them out, they're
pretty busy.

the similarity to the stm32f1 series is sufficiently strong that i
have confidence in their work, which means we can both press ahead
with firmware development whilst the usb code is moved mainline and
stabilised with unit testing.

l.