Additional includes

Author: andrjohns

stan/math/rev/core/operator_multiplication.hpp

@@ -5,6 +5,8 @@
 #include <stan/math/rev/core/var.hpp>
 #include <stan/math/rev/core/operator_addition.hpp>
 #include <stan/math/rev/core/operator_subtraction.hpp>
+#include <stan/math/rev/core/operator_plus_equal.hpp>
+#include <stan/math/rev/core/operator_minus_equal.hpp>
 #include <stan/math/rev/core/vv_vari.hpp>
 #include <stan/math/rev/core/vd_vari.hpp>
 #include <stan/math/prim/core/operator_multiplication.hpp>