5.3.8.7

* Regular Board | Gravatar support for valid e-mail address.
* Regular Board | Youtube support for video embedding (regular
youtube.com/ links or youtu.be share links).
* Regular Board | If user does not have a valid IPv4/IPv6 IP address,
posting priveliges will not be allowed and the board will be in
read-only mode.
* Navbar | Fix for category listing