pagecache: Do not write 304s to the cache.

304s are triggered in reddit by the value of a request's
If-Modified-Since header. This header is not accounted for in the
request_key. We mustn't cache a response that isn't necessarily valid
for that request.
pagecache: Make actions able to specify pagecache policies.

This allows us to control pagecache behaviour at a per-action level.
There are three policy levels,

LOGGEDIN_AND_LOGGEDOUT - allow caching of resp. generated for loggedin.
LOGGEDOUT_ONLY - the current default.
NEVER - don't use the pagecache.
pagecache: Don't cache GET_info.

Most of these results are negative lookups, so we end up spending a lot
of memcache bandwidth and memory space on identical json responses.
pagecache: Add a debug header to indicate hits/misses.

To get the header in responses, be in debug mode or send
"Pragma: x-reddit-pagecache" in your request.
Add support for a live-config sidebar info message.
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
Create Morris+Ganis
Merge pull request #787 from morrisgn/patch-1

Create Morris+Ganis
pages: Indentation fixup for admin button.
pages: Add destination parameter to adminon/off.
VDestination: Fix bug where https URLs weren't validated.
login.js: Redirect appropriately from login popup.

The login popup redirects to a link's href if one is present. This works for
all links, except for the login link which is hrefed to /login for middle
clickability. This ignores the login href specifically which results in the
current page being reloaded correctly.
redditheader.html: Reload current page on logout.
reddit_base: Optimize parsing of request_origin.