GLFW-b-3.3.9.1: TODO

Improve everything about testing.
Improve existing tests.
Add more tests.

Coordinate with GLFW C-library maintainer about any strange behavior.
1.) Cursor is in window. Left click.
    Events seen:
      cursor enter: CursorState'NotInWindow
      cursor enter: CursorState'InWindow
      mouse button: MouseButton'1 MouseButtonState'Pressed [mod keys: none]
      mouse button: MouseButton'1 MouseButtonState'Released [mod keys: none]
    The CursorState events seem spurious -- the cursor did not leave the
    window.

getPressedKeys?
getJoystickAxesN?