fix everything

Subj. But is destructing `Tox_Options` after calling `tox_new()` actually safe?

Also, should we have ipv6 turned on by default?
Wait... There's `cannot borrow immutable field `opts.txo` as mutable` on `backend::Backend::new(&mut opts.txo`... Please, don't tell me it needs `raw` method now. _Please,_ let it be not the need of method `raw`.