Fixed RenderTexture::clear() not always working on certain hardware

include/SFML/Graphics/Texture.hpp

@@ -509,6 +509,7 @@ private:
     bool         m_isSmooth;      ///< Status of the smooth filter
     bool         m_isRepeated;    ///< Is the texture in repeat mode?
     mutable bool m_pixelsFlipped; ///< To work around the inconsistency in Y orientation
+    bool         m_fboAttachment; ///< Is this texture owned by a framebuffer object?
     Uint64       m_cacheId;       ///< Unique number that identifies the texture to the render target's cache
 };