/usr/include/OGRE/RTShaderSystem/ is in libogre-1.9-dev 1.9.0+dfsg1-10.
This file is owned by root:root, with mode 0o755.
..
/usr/include/OGRE/RTShaderSystem/OgreRTShaderSystem.h
/usr/include/OGRE/RTShaderSystem/OgreShaderCGProgramProcessor.h
/usr/include/OGRE/RTShaderSystem/OgreShaderCGProgramWriter.h
/usr/include/OGRE/RTShaderSystem/OgreShaderExDualQuaternionSkinning.h
/usr/include/OGRE/RTShaderSystem/OgreShaderExHardwareSkinning.h
/usr/include/OGRE/RTShaderSystem/OgreShaderExHardwareSkinningTechnique.h
/usr/include/OGRE/RTShaderSystem/OgreShaderExIntegratedPSSM3.h
/usr/include/OGRE/RTShaderSystem/OgreShaderExLayeredBlending.h
/usr/include/OGRE/RTShaderSystem/OgreShaderExLinearSkinning.h
/usr/include/OGRE/RTShaderSystem/OgreShaderExNormalMapLighting.h
/usr/include/OGRE/RTShaderSystem/OgreShaderExPerPixelLighting.h
/usr/include/OGRE/RTShaderSystem/OgreShaderExTextureAtlasSampler.h
/usr/include/OGRE/RTShaderSystem/OgreShaderExTriplanarTexturing.h
/usr/include/OGRE/RTShaderSystem/OgreShaderFFPColour.h
/usr/include/OGRE/RTShaderSystem/OgreShaderFFPFog.h
/usr/include/OGRE/RTShaderSystem/OgreShaderFFPLighting.h
/usr/include/OGRE/RTShaderSystem/OgreShaderFFPRenderState.h
/usr/include/OGRE/RTShaderSystem/OgreShaderFFPRenderStateBuilder.h
/usr/include/OGRE/RTShaderSystem/OgreShaderFFPTexturing.h
/usr/include/OGRE/RTShaderSystem/OgreShaderFFPTransform.h
/usr/include/OGRE/RTShaderSystem/OgreShaderFunction.h
/usr/include/OGRE/RTShaderSystem/OgreShaderFunctionAtom.h
/usr/include/OGRE/RTShaderSystem/OgreShaderGLSLESProgramProcessor.h
/usr/include/OGRE/RTShaderSystem/OgreShaderGLSLESProgramWriter.h
/usr/include/OGRE/RTShaderSystem/OgreShaderGLSLProgramProcessor.h
/usr/include/OGRE/RTShaderSystem/OgreShaderGLSLProgramWriter.h
/usr/include/OGRE/RTShaderSystem/OgreShaderGenerator.h
/usr/include/OGRE/RTShaderSystem/OgreShaderHLSLProgramProcessor.h
/usr/include/OGRE/RTShaderSystem/OgreShaderHLSLProgramWriter.h
/usr/include/OGRE/RTShaderSystem/OgreShaderMaterialSerializerListener.h
/usr/include/OGRE/RTShaderSystem/OgreShaderParameter.h
/usr/include/OGRE/RTShaderSystem/OgreShaderPrerequisites.h
/usr/include/OGRE/RTShaderSystem/OgreShaderProgram.h
/usr/include/OGRE/RTShaderSystem/OgreShaderProgramManager.h
/usr/include/OGRE/RTShaderSystem/OgreShaderProgramProcessor.h
/usr/include/OGRE/RTShaderSystem/OgreShaderProgramSet.h
/usr/include/OGRE/RTShaderSystem/OgreShaderProgramWriter.h
/usr/include/OGRE/RTShaderSystem/OgreShaderProgramWriterManager.h
/usr/include/OGRE/RTShaderSystem/OgreShaderRenderState.h
/usr/include/OGRE/RTShaderSystem/OgreShaderScriptTranslator.h
/usr/include/OGRE/RTShaderSystem/OgreShaderSubRenderState.h