tty: implement binary I/O terminal mode

Introduce a uv_tty_mode_t enum for uv_tty_set_mode(), with backward
compatible values.  Add a new mode UV_TTY_MODE_IO, which uses
cfmakeraw() internally.

PR-URL: https://github.com/libuv/libuv/pull/86
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>
unix: only set SO_REUSEADDR when bind() fails

Only call setsockopt() when the initial bind() fails with EADDRINUSE,
then retry.  Saves a system call in what is normally the common case.

PR-URL: https://github.com/libuv/libuv/pull/88
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>