* path.cc (iscygdrive): Disallow /cygdrive\x.
(normalize_posix_path): "Normalize" a windows path, if detected, rather than
converting to posix.
* fhandler_serial.cc (fhandler_serial::tcsetattr): Add support and capability
checking for B230400 bitrate.
(fhandler_serial::tcgetattr): Add support for B230400 bitrate.
* include/sys/termios.h: Add B230400 definition for Posix support of 230.4Kbps.