cookie jar code: enhance security by keeping track of effective TLDs

The problem was the following: According to the cookie RFC, domains must
have at least one dot in their name for setting a cookie (e.g. domain
example.com can set a cookie for ".example.com" but not for ".com").
The problem is: Following this rule, one could still set "supercookies"
for e.g. ".co.uk".
The solution is to generate a table from
http://publicsuffix.org which maintains a list of all "effective" TLDs
like e.g. ".co.uk".

Reviewed-by: Olivier Goffart
Task-number: QTBUG-14706