add numerical recipes library

lib/nr/k_and_r/recipes/slvsm2.c

@@ -0,0 +1,14 @@
+
+#include <math.h>
+
+void slvsm2(u,rhs)
+double **rhs,**u;
+{
+	void fill0();
+	double disc,fact,h=0.5;
+
+	fill0(u,3);
+	fact=2.0/(h*h);
+	disc=sqrt(fact*fact+rhs[2][2]);
+	u[2][2] = -rhs[2][2]/(fact+disc);
+}