Ensure NS frames remain hidden when invisible

Ensure NS frames remain hidden when invisible

* nsterm.m (ns_raise_frame): only raise frame if visible.
(x_make_frame_visible): move frame to front rather than calling
ns_raise_frame().
(keyDown:) do not swallow events that aren't re-sent if frame
isn't key window.
(drawRect:) do not set visibility/iconified flags because
drawRect may be called by NSView even if the frame is hidden.

* nsfns.m (Fx_create_frame): follow other ports in
determining visibility; default to t. Ensure async_visible is set.