* Add HAVE_USB to config.mk
- Now is possible to build a usb-less version of the flasher
(only for unpacking and so, offline operations)
* Refactor varname. Avoid portability problems:
- reboot -> moboreboot
* Add new flag '-c' that makes 0xFFFF run as a shell
* Split the connect_via_usb() code from main()
* Add console handler for shell like usage of the flasher