Add support for icons in menus.
Adjustments and fixes to 4620977

- Remove Inkscape-only image-in-a-widget handler. It breaks more common
cases
- Fix up formatting to Gnome coding standards (yes, there's plenty of
other code here that needs the same treatment).
- Move nsimage_from_pixbuf() and nsimage_from_resource() to a new file
gtkosx-image.c so that they can be used in both
gtkosxapplication_quartz.c and cocoa_menu_item.c
- Introduce a new configure option, --enable-menu-images, to turn on the
feature (it's disabled by default to prevent surprises).
- Only set the image on the cocoa_item if there is one
Bump Version to 2.0.0

Reflects the changed function names to get it working with
introspection.

Also add Libtool Versioning support
Redo ChangeLog for Release 2.0.0
Fix some Gtk2 errors
Add documentation/introspection annotation for gtkosx_application_get()
Update to gtk-mac-introspection-2.0.1
Ensure HAVE_INTROSPECTION is defined

By providing a copy of introspection.m4
Bug 699987 - gtk-mac-integration build failure: can't find automake

Remove specification of old version of automake & aclocal
Update configure.ac to replace obsolete macros.
Bug 699987 - gtk-mac-integration build failure: can't find automake

Updated autogen.sh to not specify an automake version, and replaced
obsolete macros in configure.ac and Makefile.am
[Bug 698334] Mac top-of-screen menu not working properly

Fix the delay by putting a bogus event to wake up the mainloop.
Enable running test-integration without integration

To separate integration problems from underlying Gtk problems
Clean up a couple of leaks
Reformat to Gnome coding standard
Fix some Clang-5 errors
Suppress NULL object warning in cocoa_menu_item_update_accel_closure

Ensure accel_group exists before attempting to connect or disconnect
signal handlers
Revert "Suppress NULL object warning in cocoa_menu_item_update_accel_closure"

This reverts commit 32bb85d44e62a5dc3061753fa739f962b0441fb7.
Picked up too many changes...
Suppress NULL object warning in cocoa_menu_item_update_accel_closure

Ensure accel_group exists before attempting to connect or
disconnect signal handlers
Bug 703781 - app menu item disappears when made insensitive

Set the GtkMenuItem visible before calling cocoa_menu_item_add_item
in gtkosx_application_insert_app_menu_item instead of calling setHidden
on the resulting NSMenuItem, and
Override GNSMenuItem isEnabled/setEnabled to operate on the action
property instead of the enabled property. It seems that the enabled
property has no effect upon NSMenuItems in the application menu.
Provide a button to toggle the sensitivity of the preferences menu item
in test-integration.c to test the above changes.
Bug 703675 - GtkRecentChooserMenu: GtkRecentChooser doesn't work

gtk_recent_chooser_get_current_uri always returns first item in list
because it doesn't use menu item actions, it uses the menu itself and
gets the active item.

Work around this by emulating the mouse-tracking in GtkMenu with an
NSMenuDelegate responding to willHighlightItem, which tells the
GNSMenuItem to call gtk_menu_set_active to itself.

This requires keeping a reference to the GtkMenuItem on the GNSMenuItem;
we make it a GWeakRef to avoid a reference loop.

Also release submenus when they're replaced to avoid a leak.