FTDI USB driver with bitbang mode.

libFTDI is an open source library to talk to FTDI chips, including
the popular bitbang mode. The library is linked with your program in
userspace, no kernel driver required. Supported chips are:

 * FT232BM,
 * FT245BM,
 * FT2232C,
 * FT2232D,
 * FT245R,
 * FT232H,
 * FT230X.
