Skip over Ads with 0 weight
Revert "Remove memoize on normalize_hot."

This reverts commit 1dbc2b181a463828a0eda76551a1e1d1b31afeb5.
If a user is loggedin, and does not have over18 pref, do not show over18 content.

Previously, the existence of an over18 cookie would display over18 content to
loggedin users, even if their preferences disallowed over18 content.
Use the amqp message timestamp to set the Vote date.
Don't memoize cached_organic_links.
Don't memoize on get_promotion_list_cached.
API: Record account deletion time