Merge branch 'develop-olympus' into develop

* develop-olympus:
  [ticket/10158] Remove some code duplication from generating the message.
  [ticket/10195] Return false in session::check_dnsbl() when IPv6 is passed.
  [ticket/10158] Only view "Return to" links if they are useful.
  [ticket/10158] Add return-link to folder, when the user replied from a folder.
  [ticket/10158] Add "Return to Inbox"-link to "PM send"-message.

phpBB/includes/session.php

@@ -1251,6 +1251,12 @@ class session
 			$ip = $this->ip;
 		}
 
+		// Neither Spamhaus nor Spamcop supports IPv6 addresses.
+		if (strpos($ip, ':') !== false)
+		{
+			return false;
+		}
+
 		$dnsbl_check = array(
 			'sbl.spamhaus.org'	=> 'http://www.spamhaus.org/query/bl?ip=',
 		);