Feature 1255: modification in sql queries

- manage random function
    - manage regex syntax
    - manage quote (single instead of double)
    - manage interval

git-svn-id: http://piwigo.org/svn/trunk@4367 68402e56-0260-453c-a942-63ccdbb3a9ee

random.php

@@ -51,7 +51,7 @@ SELECT DISTINCT(id)
       ),
     'WHERE'
   ).'
-  ORDER BY RAND(NOW())
+  ORDER BY '.DB_RANDOM_FUNCTION.'()
   LIMIT '.min(50, $conf['top_number'],$user['nb_image_page']).'
 ;';