Point ot 6-4-stable

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Update guide for 6.3 to 6.4

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Version 6.4.0

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>