Merge: lib/serialization: fix deserialization constructor calling the default init

Restore previous behavior of the deserialization init which should not call the default init. This caused problems on default inits that accessed not yet deserialized attributes.

This also fixes WBTW troubles with game saving and multiplayer.

Pull-Request: #1766
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>