(mac_copy_area, mac_copy_area_with_mask): Restore background color.

(mac_copy_area, mac_copy_area_with_mask): Restore background color.
(mac_handle_visibility_change): New function.
(x_make_frame_invisible, x_iconify_frame)
(XTread_socket) [!USE_CARBON_EVENTS]: Use it.
[USE_CARBON_EVENTS] (mac_handle_window_event)
(install_window_handler): Handle visibilty change events.
(x_make_frame_visible): Don't reposition window if it is iconified
or asked for visible before.  Select and uncollapse window when it
is made visible.
(x_make_frame_invisible): Don't reset x_highlight_frame.
(x_iconify_frame): Likewise.  Make invisible frame visible before
it is iconified.
(read_socket_inev): Move variable outside #if USE_CARBON_EVENTS.
(do_window_update): Don't change visibility of invisible frame.