Significantly reduce the size of generated code for the opengl wrappers

Use some macro magic to declare the opengl symbols and use that
to call getProcAddress in a loop instead of doing it individually
for each method.

Cuts the amount of generated object code down from 300 to around 50k.

Change-Id: I386d278fde41a1a30827c6232e79f9156090f8b0
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

src/gui/opengl/qopenglfunctions_4_5_compatibility.cpp

@@ -3,7 +3,7 @@
 ** Copyright (C) 2015 Klaralvdalens Datakonsult AB (KDAB)
 ** Contact: https://www.qt.io/licensing/
 **
-** This file is part of the QtWidgets module of the Qt Toolkit.
+** This file is part of the QtGui module of the Qt Toolkit.
 **
 ** $QT_BEGIN_LICENSE:LGPL$
 ** Commercial License Usage