Fix PostgreSQL WHERE with boolean values
diff --git a/system/database/DB_query_builder.php b/system/database/DB_query_builder.php
index 543d5cc..00294c3 100644
--- a/system/database/DB_query_builder.php
+++ b/system/database/DB_query_builder.php
@@ -2534,7 +2534,7 @@
 	 *
 	 * Determines if a string represents a literal value or a field name
 	 *
-	 * @param	string
+	 * @param	string	$str
 	 * @return	bool
 	 */
 	protected function _is_literal($str)