iptables 1.4.21 release

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/configure.ac b/configure.ac
index 7750a3d..e83304c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,5 +1,5 @@
 
-AC_INIT([iptables], [1.4.20])
+AC_INIT([iptables], [1.4.21])
 
 # See libtool.info "Libtool's versioning system"
 libxtables_vcurrent=10