Basic demonstration of DirectInput mouse usage.  Lets you draw on the
screen with the mouse.  Note that this is not entirely well-suited
to DirectInput because the app acts pretty much like a normal Windows
application, but at least you can see how the calls are made.

This sample program demonstrates the following:

* Creating interfaces to DirectInputDevice objects.

* Acquiring and unacquiring devices.

* Reading buffered device data.

* Event notifications for device activity.

* Restricting the mouse to an arbitrary region.

* Scaling raw mouse coordinates before using them.

* Use of relative axis mode.
