add numerical recipes library

lib/nr/ansi/recipes/ellf.c

@@ -0,0 +1,14 @@
+
+#include <math.h>
+#define NRANSI
+#include "nrutil.h"
+
+float ellf(float phi, float ak)
+{
+	float rf(float x, float y, float z);
+	float s;
+
+	s=sin(phi);
+	return s*rf(SQR(cos(phi)),(1.0-s*ak)*(1.0+s*ak),1.0);
+}
+#undef NRANSI