use system header

Former-commit-id: 27c55c1b9c04798c85a32079107135ad84cb4930

include/igl/matlab/matlabinterface.h

@@ -29,7 +29,7 @@
 #include <string>
 #include <vector>
 
-#include "engine.h"  // Matlab engine header
+#include <engine.h>  // Matlab engine header
 
 namespace igl 
 {