state: report spaces in the state list parsing

This patch adds better error reporting when the user inserts a space
between two states with the --state option.

iptables -I INPUT -m state ESTABLISHED, RELATED
                                       ^
				  mind the space

results in:

iptables v1.4.2-rc1: Bad state `'
Try `iptables -h' or 'iptables --help' for more information.

Now this returns:

iptables v1.4.2-rc1: `--state' requires a list of states with no
spaces, e.g. ESTABLISHED,RELATED

This patch also applies to libxt_conntrack which has a copy of the
function.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/extensions/libxt_conntrack.c b/extensions/libxt_conntrack.c
index 3cec9dd..c7f80e0 100644
--- a/extensions/libxt_conntrack.c
+++ b/extensions/libxt_conntrack.c
@@ -107,7 +107,10 @@
 			exit_error(PARAMETER_PROBLEM, "Bad ctstate `%s'", arg);
 		arg = comma+1;
 	}
-
+	if (!*arg)
+		exit_error(PARAMETER_PROBLEM, "`--ctstate' requires a list of "
+					      "states with no spaces, e.g. "
+					      "ESTABLISHED,RELATED");
 	if (strlen(arg) == 0 || !parse_state(arg, strlen(arg), sinfo))
 		exit_error(PARAMETER_PROBLEM, "Bad ctstate `%s'", arg);
 }