add numerical recipes library

lib/nr/ansi/recipes/fredin.c

@@ -0,0 +1,10 @@
+
+float fredin(float x, int n, float a, float b, float t[], float f[],
+	float w[], float (*g)(float), float (*ak)(float, float))
+{
+	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;
+}