/usr/include/OGRE/Plugins/ is in libogre-1.9-dev 1.9.0+dfsg1-7.
This file is owned by root:root, with mode 0o755.
..
/usr/include/OGRE/Plugins/BSPSceneManager/
/usr/include/OGRE/Plugins/BSPSceneManager/OgreBspLevel.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreBspNode.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreBspPrerequisites.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreBspResourceManager.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreBspSceneManager.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreBspSceneManagerPlugin.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreBspSceneNode.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreQuake3Level.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreQuake3Shader.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreQuake3ShaderManager.h
/usr/include/OGRE/Plugins/BSPSceneManager/OgreQuake3Types.h
/usr/include/OGRE/Plugins/OctreeSceneManager/
/usr/include/OGRE/Plugins/OctreeSceneManager/OgreOctree.h
/usr/include/OGRE/Plugins/OctreeSceneManager/OgreOctreeCamera.h
/usr/include/OGRE/Plugins/OctreeSceneManager/OgreOctreeNode.h
/usr/include/OGRE/Plugins/OctreeSceneManager/OgreOctreePlugin.h
/usr/include/OGRE/Plugins/OctreeSceneManager/OgreOctreePrerequisites.h
/usr/include/OGRE/Plugins/OctreeSceneManager/OgreOctreeSceneManager.h
/usr/include/OGRE/Plugins/OctreeSceneManager/OgreOctreeSceneQuery.h
/usr/include/OGRE/Plugins/OctreeZone/
/usr/include/OGRE/Plugins/OctreeZone/OgreOctreeZone.h
/usr/include/OGRE/Plugins/OctreeZone/OgreOctreeZoneOctree.h
/usr/include/OGRE/Plugins/OctreeZone/OgreOctreeZonePlugin.h
/usr/include/OGRE/Plugins/OctreeZone/OgreOctreeZonePrerequisites.h
/usr/include/OGRE/Plugins/PCZSceneManager/
/usr/include/OGRE/Plugins/PCZSceneManager/OgreAntiPortal.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgreCapsule.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgreDefaultZone.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgrePCPlane.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgrePCZCamera.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgrePCZFrustum.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgrePCZLight.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgrePCZPlugin.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgrePCZPrerequisites.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgrePCZSceneManager.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgrePCZSceneNode.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgrePCZSceneQuery.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgrePCZone.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgrePCZoneFactory.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgrePortal.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgrePortalBase.h
/usr/include/OGRE/Plugins/PCZSceneManager/OgreSegment.h
/usr/include/OGRE/Plugins/ParticleFX/
/usr/include/OGRE/Plugins/ParticleFX/OgreAreaEmitter.h
/usr/include/OGRE/Plugins/ParticleFX/OgreBoxEmitter.h
/usr/include/OGRE/Plugins/ParticleFX/OgreBoxEmitterFactory.h
/usr/include/OGRE/Plugins/ParticleFX/OgreColourFaderAffector.h
/usr/include/OGRE/Plugins/ParticleFX/OgreColourFaderAffector2.h
/usr/include/OGRE/Plugins/ParticleFX/OgreColourFaderAffectorFactory.h
/usr/include/OGRE/Plugins/ParticleFX/OgreColourFaderAffectorFactory2.h
/usr/include/OGRE/Plugins/ParticleFX/OgreColourImageAffector.h
/usr/include/OGRE/Plugins/ParticleFX/OgreColourImageAffectorFactory.h
/usr/include/OGRE/Plugins/ParticleFX/OgreColourInterpolatorAffector.h
/usr/include/OGRE/Plugins/ParticleFX/OgreColourInterpolatorAffectorFactory.h
/usr/include/OGRE/Plugins/ParticleFX/OgreCylinderEmitter.h
/usr/include/OGRE/Plugins/ParticleFX/OgreCylinderEmitterFactory.h
/usr/include/OGRE/Plugins/ParticleFX/OgreDeflectorPlaneAffector.h
/usr/include/OGRE/Plugins/ParticleFX/OgreDeflectorPlaneAffectorFactory.h
/usr/include/OGRE/Plugins/ParticleFX/OgreDirectionRandomiserAffector.h
/usr/include/OGRE/Plugins/ParticleFX/OgreDirectionRandomiserAffectorFactory.h
/usr/include/OGRE/Plugins/ParticleFX/OgreEllipsoidEmitter.h
/usr/include/OGRE/Plugins/ParticleFX/OgreEllipsoidEmitterFactory.h
/usr/include/OGRE/Plugins/ParticleFX/OgreHollowEllipsoidEmitter.h
/usr/include/OGRE/Plugins/ParticleFX/OgreHollowEllipsoidEmitterFactory.h
/usr/include/OGRE/Plugins/ParticleFX/OgreLinearForceAffector.h
/usr/include/OGRE/Plugins/ParticleFX/OgreLinearForceAffectorFactory.h
/usr/include/OGRE/Plugins/ParticleFX/OgreParticleFXPlugin.h
/usr/include/OGRE/Plugins/ParticleFX/OgreParticleFXPrerequisites.h
/usr/include/OGRE/Plugins/ParticleFX/OgrePointEmitter.h
/usr/include/OGRE/Plugins/ParticleFX/OgrePointEmitterFactory.h
/usr/include/OGRE/Plugins/ParticleFX/OgreRingEmitter.h
/usr/include/OGRE/Plugins/ParticleFX/OgreRingEmitterFactory.h
/usr/include/OGRE/Plugins/ParticleFX/OgreRotationAffector.h
/usr/include/OGRE/Plugins/ParticleFX/OgreRotationAffectorFactory.h
/usr/include/OGRE/Plugins/ParticleFX/OgreScaleAffector.h
/usr/include/OGRE/Plugins/ParticleFX/OgreScaleAffectorFactory.h