Facilitate creation and usage of boards with "." and "+" characters in name.

This commit is mostly work in progress, will be rewritten.

inc/functions.php

@@ -1436,7 +1436,7 @@ function markup(&$body, $track_cites = false) {
 	}
 	
 	// Cross-board linking
-	if (preg_match_all('/(^|\s)>>>\/(\w+?)\/(\d+)?([\s,.)?]|$)/m', $body, $cites)) {
+	if (preg_match_all('/(^|\s)>>>\/([\w.+]+?)\/(\d+)?([\s,.)?]|$)/m', $body, $cites)) {
 		if (count($cites[0]) > $config['max_cites']) {
 			error($config['error']['toomanycross']);
 		}