APP: Major changes in an interface driver code.
Interface driver (structure) now contains all necessary functions to operate.
This is important for drivers other than using libftdi, they are now possible.
Existing functions based on libftdi were renamed to contain "ftdi" string.
This change makes it possible to experiment with new async libusb1 interface,
that would talk to FTDI chip directly and hopefully will increase performance.
LibSWD driver bridge now use function pointers from interface structure,
these are "bitbang", "transfer_bits" and "transfer_bytes".
libswd_driver_t was extended with (void*)interface field to hold the routines.