use new doublearea

Former-commit-id: 63859c11d38141b123cfa13d4d7991bd32d98bf5

include/igl/collapse_small_triangles.cpp

@@ -31,7 +31,7 @@ void igl::collapse_small_triangles(
   MatrixXd l;
   edge_lengths(V,F,l);
   VectorXd dblA;
-  doublearea(l,dblA);
+  doublearea(l,0.,dblA);
 
   // Minimum area tolerance
   const double min_dblarea = 2.0*eps*bbd*bbd;