(x_draw_fringe_bitmap) [MAC_OSX]: Extend fringe

(x_draw_fringe_bitmap) [MAC_OSX]: Extend fringe
background to scroll bar gap.
(x_scroll_bar_create) [MAC_OSX]: Set bar->fringe_extended_p.
(XTset_vertical_scroll_bar) [MAC_OSX]: Put leftmost/rightmost
scroll bars on frame edge.  Check fringe background extension.
Don't clear extended fringe background area.
(TOOLBAR_IDENTIFIER, TOOLBAR_ICON_ITEM_IDENTIFIER)
(TOOLBAR_ITEM_COMMAND_ID_OFFSET, TOOLBAR_ITEM_COMMAND_ID_P)
(TOOLBAR_ITEM_COMMAND_ID_VALUE, TOOLBAR_ITEM_MAKE_COMMAND_ID):
[USE_MAC_TOOLBAR]: New macros.
(mac_move_window_with_gravity, mac_get_window_origin_with_gravity)
(mac_handle_toolbar_event, mac_image_spec_to_cg_image)
(mac_create_frame_tool_bar, update_frame_tool_bar, free_frame_tool_bar)
(mac_tool_bar_note_mouse_movement, mac_handle_toolbar_command_event)
[USE_MAC_TOOLBAR]: New functions.
(mac_handle_window_event) [USE_MAC_TOOLBAR]: Reposition window
manually if previous repositioning has failed.
(mac_handle_keyboard_event): Use precomputed event kind.
(XTread_socket) [USE_MAC_TOOLBAR]: Handle click in structure region
as tool bar item click.  Handle mouse movement over tool bar items.