add numerical recipes library

lib/nr/cpp/recipes/polin2.cpp

@@ -0,0 +1,16 @@
+#include "nr.h"
+
+void NR::polin2(Vec_I_DP &x1a, Vec_I_DP &x2a, Mat_I_DP &ya, const DP x1,
+	const DP x2, DP &y, DP &dy)
+{
+	int j,k;
+
+	int m=x1a.size();
+	int n=x2a.size();
+	Vec_DP ymtmp(m),ya_t(n);
+	for (j=0;j<m;j++) {
+		for (k=0;k<n;k++) ya_t[k]=ya[j][k];
+		polint(x2a,ya_t,x2,ymtmp[j],dy);
+	}
+	polint(x1a,ymtmp,x1,y,dy);
+}