/usr/include/OGRE/RenderSystems/GL/ is in libogre-1.8-dev 1.8.1+dfsg-0ubuntu3.
This file is owned by root:root, with mode 0o755.
..
/usr/include/OGRE/RenderSystems/GL/GL/
/usr/include/OGRE/RenderSystems/GL/GL/gl.h
/usr/include/OGRE/RenderSystems/GL/GL/glew.h
/usr/include/OGRE/RenderSystems/GL/GL/glext.h
/usr/include/OGRE/RenderSystems/GL/GL/glxew.h
/usr/include/OGRE/RenderSystems/GL/GL/glxext.h
/usr/include/OGRE/RenderSystems/GL/GL/glxtokens.h
/usr/include/OGRE/RenderSystems/GL/GL/wglew.h
/usr/include/OGRE/RenderSystems/GL/GL/wglext.h
/usr/include/OGRE/RenderSystems/GL/GLX/
/usr/include/OGRE/RenderSystems/GL/GLX/OgreGLUtil.h
/usr/include/OGRE/RenderSystems/GL/GLX/OgreGLXContext.h
/usr/include/OGRE/RenderSystems/GL/GLX/OgreGLXGLSupport.h
/usr/include/OGRE/RenderSystems/GL/GLX/OgreGLXRenderTexture.h
/usr/include/OGRE/RenderSystems/GL/GLX/OgreGLXUtils.h
/usr/include/OGRE/RenderSystems/GL/GLX/OgreGLXWindow.h
/usr/include/OGRE/RenderSystems/GL/OgreGLATIFSInit.h
/usr/include/OGRE/RenderSystems/GL/OgreGLContext.h
/usr/include/OGRE/RenderSystems/GL/OgreGLDefaultHardwareBufferManager.h
/usr/include/OGRE/RenderSystems/GL/OgreGLDepthBuffer.h
/usr/include/OGRE/RenderSystems/GL/OgreGLFBOMultiRenderTarget.h
/usr/include/OGRE/RenderSystems/GL/OgreGLFBORenderTexture.h
/usr/include/OGRE/RenderSystems/GL/OgreGLFrameBufferObject.h
/usr/include/OGRE/RenderSystems/GL/OgreGLGpuNvparseProgram.h
/usr/include/OGRE/RenderSystems/GL/OgreGLGpuProgram.h
/usr/include/OGRE/RenderSystems/GL/OgreGLGpuProgramManager.h
/usr/include/OGRE/RenderSystems/GL/OgreGLHardwareBufferManager.h
/usr/include/OGRE/RenderSystems/GL/OgreGLHardwareIndexBuffer.h
/usr/include/OGRE/RenderSystems/GL/OgreGLHardwareOcclusionQuery.h
/usr/include/OGRE/RenderSystems/GL/OgreGLHardwarePixelBuffer.h
/usr/include/OGRE/RenderSystems/GL/OgreGLHardwareVertexBuffer.h
/usr/include/OGRE/RenderSystems/GL/OgreGLPBRenderTexture.h
/usr/include/OGRE/RenderSystems/GL/OgreGLPBuffer.h
/usr/include/OGRE/RenderSystems/GL/OgreGLPixelFormat.h
/usr/include/OGRE/RenderSystems/GL/OgreGLPlugin.h
/usr/include/OGRE/RenderSystems/GL/OgreGLPrerequisites.h
/usr/include/OGRE/RenderSystems/GL/OgreGLRenderSystem.h
/usr/include/OGRE/RenderSystems/GL/OgreGLRenderTexture.h
/usr/include/OGRE/RenderSystems/GL/OgreGLRenderToVertexBuffer.h
/usr/include/OGRE/RenderSystems/GL/OgreGLSLExtSupport.h
/usr/include/OGRE/RenderSystems/GL/OgreGLSLGpuProgram.h
/usr/include/OGRE/RenderSystems/GL/OgreGLSLLinkProgram.h
/usr/include/OGRE/RenderSystems/GL/OgreGLSLLinkProgramManager.h
/usr/include/OGRE/RenderSystems/GL/OgreGLSLPreprocessor.h
/usr/include/OGRE/RenderSystems/GL/OgreGLSLProgram.h
/usr/include/OGRE/RenderSystems/GL/OgreGLSLProgramFactory.h
/usr/include/OGRE/RenderSystems/GL/OgreGLSupport.h
/usr/include/OGRE/RenderSystems/GL/OgreGLTexture.h
/usr/include/OGRE/RenderSystems/GL/OgreGLTextureManager.h