Added initial support for canusb devices.

Added initial support for canusb devices.

CanUSB devices are not directly supported by the kernel.
LibUSB-1.0 is used to communicate them, with a special protocol.

Reading 2 bytes from interrupt endpoint 1 returns the number of packets in the
rx and the tx buffer,

Reading 20 bytes from bulk endpoint 5 returns a 4byte timestamp in 10us
resolution since powerup, and a can fram in socket_can frame format, so
DLT_SOCKETCAN may be used.

TODO: use async libusb communication