* editfns.c (Voperating_system_release): Added.

* editfns.c (Voperating_system_release): Added.
	(init_editfns): Assign new variable operating-system-release
	based on call to uname if available.
	(get_operating_system_release): Added function to
	allow c-level access to operating system release.
* config.h: Regenerated.
* s/darwin.h (PTY_ITERATION): Don't allow PTYs on darwin 6 or
	less.
	(MIN_PTY_KERNEL_VERSION): Defined minimum kernel version for
	using ptys as '7'.
* term/mac-win.el (process-connection-type): Removed.
	Controlled now by s/darwin.h:PTY_ITERATION.