Window resize fixes

- Track mouse exit from window resize rect instead of unconditionally setting arrow cursor.
- Don't show the resize cursors for full platform windows.
- Show the resize down cursor if the top of a window is being resized and it has reached the bottom of the menubar.
- Make windows in CPToolbarTest resizable to test resizing behavior with toolbars.
- Added a full platform window and menubar to the test app.