missing header

Former-commit-id: 5b4bfd6ba7bfa969de69ff0ba5181a877b725d06

include/igl/xml/write_triangle_mesh.cpp

@@ -7,6 +7,7 @@
 // obtain one at http://mozilla.org/MPL/2.0/.
 #include "write_triangle_mesh.h"
 #include "../write_triangle_mesh.h"
+#include "../pathinfo.h"
 #include "writeDAE.h"
 
 template <typename DerivedV, typename DerivedF>