IWYU reported header updates

src/math_eigen.cpp

@@ -18,7 +18,9 @@
 #include "math_eigen.h"
 #include "math_eigen_impl.h"
 
-#include<array>
+#include <array>
+#include <utility>
+#include <vector>
 
 using std::vector;
 using std::array;