Move Element::setNeighbor() into private section.

MeshLib/Elements/Element.h

@@ -39,8 +39,6 @@ public:
 	/// Compute the minimum and maximum squared edge length for this element
 	virtual void computeSqrEdgeLengthRange(double &min, double &max) const;
 
-	void setNeighbor(Element* neighbor, unsigned const face_id);
-
 	/**
 	 * \brief Tries to add an element e as neighbour to this element.
 	 * If the elements really are neighbours, the element is added to the
@@ -210,6 +208,10 @@ protected:
 	 */
 	unsigned _value;
 	Element** _neighbors;
+	/// Sets the neighbor over the face with \c face_id to the given \c
+	/// neighbor.
+	void setNeighbor(Element* neighbor, unsigned const face_id);
+
 }; /* class */
 
 } /* namespace */