This allows a new state to disallow resizing the window but allow
making the window fullscreen on macOS by a user.
This change adds the new type WindowResizingModeType. There are
these constants of this type:
* WindowResizingModeDisabled
* WindowResizingModeOnlyFullscreenEnabled
* WindowResizingModeEnabled
Closes#1819
Unfortunately, it is almost impossible to provide a consistent behavior
to keep the aspect ratio of the window on Windows. Instead of having an
incomplete API, let's remove this.
Closes#1988
