fix vertex->edge adjacency when reading msh (v4) files

src/geo/GEdge.h

@@ -58,8 +58,8 @@ public:
   virtual void deleteMesh();
 
   // get the start/end vertices of the edge
-  void setBeginVertex(GVertex *gv) { _v0 = gv; }
-  void setEndVertex(GVertex *gv) { _v1 = gv; }
+  void setBeginVertex(GVertex *gv) { _v0 = gv; gv->addEdge(this);}
+  void setEndVertex(GVertex *gv) { _v1 = gv;  gv->addEdge(this);}
   virtual GVertex *getBeginVertex() const { return _v0; }
   virtual GVertex *getEndVertex() const { return _v1; }
   void setVertex(GVertex *const f, const int orientation)