doc: make netmasks in 4.3 Static Route Commands the same

In 4.3 documentation shows example for defining static routes:
--------------------------------------------------------------
  ip route 10.0.0.0/8 10.0.0.2
  (...)
  ip route 10.0.0.0 255.255.255.0 10.0.0.2
  (...)
  These statements are equivalent to those in the previous example.
--------------------------------------------------------------

10.0.0.0/8 is not equivalent to 10.0.0.0/255.255.255.0, fix it.

should fix #811 after html regenerating.
diff --git a/doc/main.texi b/doc/main.texi
index 0874c5c..849773b 100644
--- a/doc/main.texi
+++ b/doc/main.texi
@@ -177,9 +177,9 @@
 format.  @var{gateway} is same option as above command
 
 @example
-ip route 10.0.0.0 255.255.255.0 10.0.0.2
-ip route 10.0.0.0 255.255.255.0 ppp0
-ip route 10.0.0.0 255.255.255.0 null0
+ip route 10.0.0.0 255.0.0.0 10.0.0.2
+ip route 10.0.0.0 255.0.0.0 ppp0
+ip route 10.0.0.0 255.0.0.0 null0
 @end example
 
 These statements are equivalent to those in the previous example.