add numerical recipes library

lib/nr/k_and_r/recipes/fredin.c

@@ -0,0 +1,11 @@
+
+float fredin(x,n,a,b,t,f,w,g,ak)
+float (*ak)(),(*g)(),a,b,f[],t[],w[],x;
+int n;
+{
+	int i;
+	float sum=0.0;
+
+	for (i=1;i<=n;i++) sum += (*ak)(x,t[i])*w[i]*f[i];
+	return (*g)(x)+sum;
+}