Adding missing files

src/interpolation/mp4_kernel.hpp

+/*
+ * mp4_kernel.hpp
+ *
+ *  Created on: May 5, 2017
+ *      Author: i-bird
+ */
+
+#ifndef OPENFPM_NUMERICS_SRC_INTERPOLATION_MP4_KERNEL_HPP_
+#define OPENFPM_NUMERICS_SRC_INTERPOLATION_MP4_KERNEL_HPP_
+
+#include <iostream>
+
+template<typename st>
+class mp4_kernel
+{
+public:
+
+	static const int np = 4;
+
+	static inline st value(st x, size_t i)
+	{
+		if (i == 0)
+			return st(2.0) + (st(-4.0)+(st(2.5)-st(0.5)*-x)*-x)*-x;
+		else if (i == 1)
+			return st(1.0) + (st(-2.5)+st(1.5)*-x)*x*x;
+		else  if (i == 2)
+			return st(1.0) + (st(-2.5)+st(1.5)*x)*x*x;
+		else if (i == 3)
+			return st(2.0) + (st(-4.0)+(st(2.5)-st(0.5)*x)*x)*x;
+		return 0.0;
+	}
+};
+
+#endif /* OPENFPM_NUMERICS_SRC_INTERPOLATION_MP4_KERNEL_HPP_ */