Add type 'ident' in quote() so we can quote identifiers (eg. column names) there.

Using array2list() for list of identifiers is now possible.

program/lib/Roundcube/rcube_db.php

@@ -571,7 +571,7 @@ class rcube_db
      * Formats input so it can be safely used in a query
      *
      * @param mixed  $input Value to quote
-     * @param string $type  Type of data
+     * @param string $type  Type of data (integer, bool, ident)
      *
      * @return string Quoted/converted string for use in query
      */
@@ -586,6 +586,10 @@ class rcube_db
             return 'NULL';
         }
 
+        if ($type == 'ident') {
+            return $this->quote_identifier($input);
+        }
+
         // create DB handle if not available
         if (!$this->dbh) {
             $this->db_connect('r');
@@ -652,7 +656,7 @@ class rcube_db
      * Return list of elements for use with SQL's IN clause
      *
      * @param array  $arr  Input array
-     * @param string $type Type of data
+     * @param string $type Type of data (integer, bool, ident)
      *
      * @return string Comma-separated list of quoted values for use in query
      */