- Make escape sequence to exit tty optional since we want to reuse
  lxc_console_cb_tty_stdin() in lxc_attach.c.
- Export the following functions since they can be reused in other modules:
  - lxc_console_cb_tty_stdin()
  - lxc_console_cb_tty_master()
  - lxc_setup_tios(int fd, struct termios *oldtios);
  - lxc_console_winsz(int srcfd, int dstfd);
  - lxc_console_cb_sigwinch_fd(int fd, uint32_t events, void *cbdata, struct lxc_epoll_descr *descr);
  - lxc_tty_state *lxc_console_sigwinch_init(int srcfd, int dstfd);
  - lxc_console_sigwinch_fini(struct lxc_tty_state *ts);
- rewrite lxc_console_set_stdfds()
  - Make lxc_console_set_stdfds useable by other callers that do not have
    access to lxc_handler.
- Use ssh settings for ptys.
- Remove all asserts from console.{c,h}.
- Adapt start.c to changes.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>