The attached hack fixes a problem which occurs since
switching the pty code.  isatty() hangs if the slave_fd
is closed and reopened as in the deprecated APIs
pty.master_open() and pty.slave_open().

This patch reverts to the old behaviour where
_open_terminal() is called in master_open() to avoid
the hang later.

Here's a very simple test for the problem:

import pty, os

master_fd, slave_name = pty.master_open()
slave_fd = pty.slave_open(slave_name)
print os.isatty(slave_fd)

In slave_open() the first ioctl raises an IOError,
Invalid Argument 22.

I don't know if this problem affects hpux10.  Hopefully
someone will have a better idea how to really fix this
problem.