add numerical recipes library

lib/nr/ansi/recipes/rsolv.c

@@ -0,0 +1,12 @@
+
+void rsolv(float **a, int n, float d[], float b[])
+{
+	int i,j;
+	float sum;
+
+	b[n] /= d[n];
+	for (i=n-1;i>=1;i--) {
+		for (sum=0.0,j=i+1;j<=n;j++) sum += a[i][j]*b[j];
+		b[i]=(b[i]-sum)/d[i];
+	}
+}