|SOURCE|
[Common::Renderer::OGL::GLExtender]
* Added zglReadPixels
[Common::Renderer::Renderer]
* Added a screenshot utility to save the back buffer when the next frame has
  finished rendering
[Linux::Renderer::LinuxRendererOGL3]
* EndScene renders the contents of the back buffer to a file "test.tga"
* Create associates the backbuffer ID with an area of memory which OpenGL can
  write to for taking screenshots
|SOURCE|
[Common::Renderer::OGL::GLExtender]
* Added zglReadBuffer
[Linux::Renderer::LinuxRendererOGL3]
* Added a member variable to keep track of the screenshot file name
* EndScene uses the screenshot file name member variable to write out the
  screenshot to disk
* If either the header or the image data for the Targa screenshot fail to
  write, the file is closed and the GL_PIXEL_PACK_BUFFER_ARB is set to zero
  before returning
* Screenshot takes into account the relative to executable directory value and
  will use this to write the screenshot to the correct directory