Summary:
The new tab shows the information from GLPlatform similar to how it is
shown in the supportInformation. In addition it also lists all available
openGL and EGL/GLX extensions. For that kwinglutils is extended by
functions to return the lists of extensions.

Reviewers: #kwin, #plasma, bshah

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D2385