export: Pre-fetch staff objects

This is required because using unbuffered MySQL queries means that no other
SQL queries can be run until the export is finished. Since the Staff model
will lazily query the config table, the queries need to be fetched in
advance.

include/class.export.php

@@ -75,6 +75,11 @@ class Export {
                     ->aggregate(array('count' => SqlAggregate::COUNT('entries__id'))),
             ));
 
+        // Fetch staff information
+        // FIXME: Adjust Staff model so it doesn't do extra queries
+        foreach (Staff::objects() as $S)
+            $S->get('junk');
+
         return self::dumpQuery($tickets,
             array(
                 'number' =>         __('Ticket Number'),