is_charged_transaction: refunded is still charged.
Allow subtracting subreddits from /r/mod.
AllMinus/ModMinus: Handle case where base_sr doesn't exist.
Link._by_url: always return a list.
hot_links_by_url_listing: Return a listing of links for a given url.
VUrl: Don't check for already submitted url.
Delete link_from_url and filter_links.
Only demangle_url if there is a url.
Ignore case when building list of subreddits with saved things.
Make all moderators have a modmsgtime attribute.

This attribute can serve as a handy indicator that a user is a moderator
somewhere and can therefore replace the more costly modship lookup in
reddit_base.