/usr/include/crystalspace-2.0/csplugincommon/opengl/ is in libcrystalspace-dev 2.0+dfsg-1build1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/crystalspace-2.0/csplugincommon/opengl/assumedstate.h
/usr/include/crystalspace-2.0/csplugincommon/opengl/csextern_gl.h
/usr/include/crystalspace-2.0/csplugincommon/opengl/driverdb.h
/usr/include/crystalspace-2.0/csplugincommon/opengl/glcommon2d.h
/usr/include/crystalspace-2.0/csplugincommon/opengl/glenum_identstrs.h
/usr/include/crystalspace-2.0/csplugincommon/opengl/glextmanager.h
/usr/include/crystalspace-2.0/csplugincommon/opengl/glfontcache.h
/usr/include/crystalspace-2.0/csplugincommon/opengl/glhelper.h
/usr/include/crystalspace-2.0/csplugincommon/opengl/glss.h
/usr/include/crystalspace-2.0/csplugincommon/opengl/glstates.h
/usr/include/crystalspace-2.0/csplugincommon/opengl/shaderplugin.h