Merge branch 'master' into testing

classes/kohana/validate.php

@@ -352,7 +352,7 @@ public static function digit($str, $utf8 = FALSE)
 		}
 		else
 		{
-			return is_int($str) OR ctype_digit($str);
+			return (is_int($str) AND $str >= 0) OR ctype_digit($str);
 		}
 	}