add numerical recipes library

lib/nr/ansi/recipes/chint.c

@@ -0,0 +1,16 @@
+
+void chint(float a, float b, float c[], float cint[], int n)
+{
+	int j;
+	float sum=0.0,fac=1.0,con;
+
+	con=0.25*(b-a);
+	for (j=1;j<=n-2;j++) {
+		cint[j]=con*(c[j-1]-c[j+1])/j;
+		sum += fac*cint[j];
+		fac = -fac;
+	}
+	cint[n-1]=con*c[n-2]/(n-1);
+	sum += fac*cint[n-1];
+	cint[0]=2.0*sum;
+}