preg_quote() the permalink structure so that regex special chars such as dots are correctly handled. Props SergeyBiryukov. fixes #21167

git-svn-id: https://develop.svn.wordpress.org/trunk@22365 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/rewrite.php

@@ -1251,6 +1251,8 @@ class WP_Rewrite {
 			}
 		}
 
+		$permalink_structure = preg_quote( $permalink_structure );
+
 		//get everything up to the first rewrite tag
 		$front = substr($permalink_structure, 0, strpos($permalink_structure, '%'));
 		//build an array of the tags (note that said array ends up being in $tokens[0])