Log Message:
Update to libftdi-0.19.

Changes since 0.18:
- Make kernel driver detach configurable (Thomas Klose)
- Correct ftdi_poll_modem_status() result code (Tom Saunders)
- cmake build system improvements (Evgeny Sinelnikov)
- Fix uninitialized memory access in async mode (Intra2net)
- Support for FT232R eeprom features (Hermann Kraus)
- Fix size returned by ftdi_read_data (Hermann Kraus)
- C++ wrapper: Fix infinite recursion in set_bitmode (Intra2net)
- Improvements to the python wrapper (Flynn Marquardt and Chris Zeh)