Change the default major version of QGLFormat to 2.

This is being changed because:
- The OpenGL paint engine in Qt only supports GL2
- QML2 only supports GL2
- QSurfaceFormat has a default value of 2

Applications that want to use GL1 on a QGLWidget will have to
explicitly request this format using QGLFormat::setVersion.

Task-number: QTBUG-27589

Change-Id: Ieb283ef7d6e15a29ec28ce7e4363dbf477decaa7
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

dist/changes-5.0.0

@@ -617,6 +617,9 @@ QtOpenGL
   QGLWidget and a QOpenGLFramebufferObject. It is recommended that applications
   using QGLPixelBuffer for offscreen rendering to a texture switch to using
   QOpenGLFramebufferObject directly instead, for improved performance.
+* The default major version of QGLFormat has been changed to 2 to be aligned
+  with QSurfaceFormat. Applications that want to use a different version should
+  explicitly request it using QGLFormat::setVersion().
 
 QtScript
 --------

src/opengl/qgl_p.h

@@ -86,7 +86,7 @@ public:
         depthSize = accumSize = stencilSize = redSize = greenSize = blueSize = alphaSize = -1;
         numSamples = -1;
         swapInterval = -1;
-        majorVersion = 1;
+        majorVersion = 2;
         minorVersion = 0;
         profile = QGLFormat::NoProfile;
     }

tests/auto/opengl/qgl/tst_qgl.cpp

@@ -439,7 +439,7 @@ void tst_QGL::getSetCheck()
 
     // int QGLFormat::major/minorVersion()
     // void QGLFormat::setVersion(int, int)
-    QCOMPARE(obj1.majorVersion(), 1);
+    QCOMPARE(obj1.majorVersion(), 2);
     QCOMPARE(obj1.minorVersion(), 0);
     obj1.setVersion(3, 2);
     QCOMPARE(obj1.majorVersion(), 3);