Fix for compiling and running cube example on Windows.

Change-Id: I0bf933fe81e332c03a81874cb371fa423634621b
Reviewed-on: http://codereview.qt.nokia.com/125
Reviewed-by: David Boddie

examples/opengl/cube/geometryengine.cpp

@@ -21,6 +21,8 @@ GeometryEngine::~GeometryEngine()
 
 void GeometryEngine::init()
 {
+    initializeGLFunctions();
+
 //! [0]
     // Generate 2 VBOs
     glGenBuffers(2, vboIds);

examples/opengl/cube/mainwidget.cpp

@@ -78,6 +78,8 @@ void MainWidget::timerEvent(QTimerEvent *e)
 
 void MainWidget::initializeGL()
 {
+    initializeGLFunctions();
+
     qglClearColor(Qt::black);
 
     qDebug() << "Initializing shaders...";

examples/opengl/cube/mainwidget.h

@@ -2,6 +2,7 @@
 #define MAINWIDGET_H
 
 #include <QtOpenGL/QGLWidget>
+#include <QtOpenGL/QGLFunctions>
 
 #include <QMatrix4x4>
 #include <QQuaternion>
@@ -12,7 +13,7 @@ class QGLShaderProgram;
 
 class GeometryEngine;
 
-class MainWidget : public QGLWidget
+class MainWidget : public QGLWidget, protected QGLFunctions
 {
     Q_OBJECT
 public: