Choose cookie domain

[AzariasB]

I have a website using several sub-domains for translation purposes (fr.exemple.com, en.exemple.com, ...) whenever the user accepts the cookies on one domain, it would be great if it could set the domain to the root domain (or to a choice domain) to avoid having to ask to accept the cookies on every sub-domain. I could do a pull request if needed to add this feature :)