Examples from "OpenGL Tutorial" by Digia (2013)
This series of commits implements all examples from "OpenGL Tutorial,
Release 1.0" by Digia, Qt Learning from February 28, 2013; examples use
Qt5 and QGLWidget.
http://ftp.fau.de/qtproject/learning/developerguides/qtopengltutorial/
Relevant parts from the table of contents of this tutorial:
3 Using OpenGL in your Qt Application
3.1 Hello OpenGL
3.2 Rendering in 3D
3.3 Coloring
3.4 Texture Mapping
3.5 Lighting
3.6 Buffer Object