|SOURCE|
[Common::Renderer::OGL::GLExtender]
* Removed windowing system specific data types, instead the
  ZED::System::WINDOWDATA struct is used to make it simpler for the user
  calling member functions and the constructor to pass in this struct instead
  of one or more windowing system specific types
* InitialiseWindowExtensions no longer accepts any parameters
[Linux::Renderer::GLExtender]
* The constructor taking in a ZED::System::WINDOWDATA structure assigns it to
  the window data attribute
* InitialiseWindowExtensions uses the window data attribute to find the
  window's GLX extensions
[Common::Renderer::OGL::GLRenderTypes]
* Included the GL/gl.h header file, before it was using other header files
  included before it to include this file
[Linux::Renderer::LinuxRendererOGL3]
* Forward-declared GLExtender and GLVertexCacheManager
* The GLExtender attribute is now a pointer, as the constructor'a parameter
  list is not empty
|MERGE|
renderer_glextender merged into unstable