merge -r 2094 from branch-1_7 to trunk

- fix: quick search error if the query term contained " or '
- optimized sql query in sync_users (called every time on admin page) - a lot faster when #user_cache_categories is big
- added function Template->delete_block_vars (opposite of assign_block_vars)

git-svn-id: http://piwigo.org/svn/trunk@2095 68402e56-0260-453c-a942-63ccdbb3a9ee

qsearch.php

@@ -43,7 +43,7 @@ $query ='
 INSERT INTO '.SEARCH_TABLE.'
   (rules, last_seen)
   VALUES
-  (\''.serialize($search).'\', NOW() )
+  (\''.addslashes(serialize($search)).'\', NOW() )
 ;';
 pwg_query($query);