The main advantage of SPDX license identifiers over the traditional
license headers is that it's more difficult to overlook inappropriate
licenses for kwin, for example GPL 3. We also don't have to copy a
lot of boilerplate text.
In order to create this change, I ran licensedigger -r -c from the
toplevel source directory.
The SceneOpenGLTest is transformed into a GenericSceneOpenGLTest which
can create either an OpenGL or an OpenGL ES scene based on env variable
which it sets in initTestCase. The env variable to set is passed as a
ctor argument from the SceneOpenGLTest and the new SceneOpenGLESTest.
This allows to easily run the same test code for both our OpenGL and
OpenGL ES compositor.