add numerical recipes library

lib/nr/ansi/recipes/qgaus.c

@@ -0,0 +1,19 @@
+
+float qgaus(float (*func)(float), float a, float b)
+{
+	int j;
+	float xr,xm,dx,s;
+	static float x[]={0.0,0.1488743389,0.4333953941,
+		0.6794095682,0.8650633666,0.9739065285};
+	static float w[]={0.0,0.2955242247,0.2692667193,
+		0.2190863625,0.1494513491,0.0666713443};
+
+	xm=0.5*(b+a);
+	xr=0.5*(b-a);
+	s=0;
+	for (j=1;j<=5;j++) {
+		dx=xr*x[j];
+		s += w[j]*((*func)(xm+dx)+(*func)(xm-dx));
+	}
+	return s *= xr;
+}