Extensive refactoring of the demo.
Extensive refactoring of the demo.

Removed unnecessary ifdef's, Qt takes care of resize() and showFullScreen().
Simplified include statements as this is just an example.
paintEvent only blits internal bitmap to avoid animation acceleration.
Simplified event handling, and hopefully more readable now.
The demo can now be embedded in any app, be stopped/restarted, set frame rate.
Use of QBasicTimer instead of QTimer improved performance.
Painting to internal bitmap is now done in timerEvent.

Additional features:
- Use Space key to toggle animation.
- Use 'O' and 'P' to decrease and increase the frame rate, respectively.

ariya/X2,ariya/X2,ariya/X2