* we allow tty_driver to cover more than 256 devices
	* pty.c cleaned up - now we only one driver for UNIX98 masters and
only one driver for UNIX98 slaves, so a lot of ugliness can be killed.
	* get_tty_driver() became an analog of get_gendisk() - it does
a lookup by device number and gives (pointer to tty_driver,index).
	* registration/unregistration of tty_driver updated
	* /proc/tty/drivers code updated (now one structure can be responsible
for several lines)