Remove nonstandard O_NONBLOCK flag from posix_openpt() call
Remove nonstandard O_NONBLOCK flag from posix_openpt() call

Including the O_NONBLOCK flag in our posix_openpt() call was resulting
in an error on FreeBSD, as this is not a standard flag according to
the POSIX specification.  Instead, we now specify O_NONBLOCK using
fcntl() after opening the PTY master.

markshroyer/nulltty,markshroyer/nulltty