Fix for ticket #2942: character counter now updates on cut and paste operations made with mouse or menu

This uses the 'copy' and 'paste' DOM events to trigger a counter update. I haven't had a chance to 100% confirm that middle-button click on X11 triggers the event, but it ought to.
Cut and paste events from context menu and main edit menu known good in:
* Firefox 4.08b-pre
* IE 9 preview 7
* IE 8 current
* Chrome 8 beta current
* Safari 5.0.3

Opera is listed as not supporting these events, oh well.

Note that using a *delete* command from a menu doesn't trigger an event. Sigh, you can't win everything.

Cleaner code to avoid a couple PHP notices from accessing uninitialized variables in ostatus profile discovery (these cases hit checking diaspora accounts)

Mark OembedAction, XrdAction, and (plugin) AutocompleteAction as read-only. Tweaked ApiStatusesShow and ApiTimelineUser to still claim read-only when hit with a HEAD request (usually link checkers or a precursor to a GET, and should be semantically equivalent to a GET without actually transferring data)

Router entry for AtomPubService was slightly off, generating an incorrect link in the RSD data.

AtomPub test cases: make sure the posted entry appears in the feed, and that it disappears after deletion

AtomPub fix: correct the response URL given from posting a new message (wrong parameter meant we got the main page instead of the message's URL)

TwitterBridge: partial merge of id_str usage from 0.9.x for improved 32-bit and pre-5.2.10 compatibility. (on 64-bit in 5.2.6 we can pull the integer IDs, but silently lose some precision on the end.)

Fixes for Twitter bridge breakage on 32-bit servers. New "Snowflake" 64-bit IDs have become too big to fit in the integer portion of double-precision floats, so to reliably use these IDs we need to pull the new string form now.
Machines with 64-bit PHP installation should have had no problems (except on Windows, where integers are still 32 bits)

Conflicts:

	plugins/TwitterBridge/twitterimport.php <- as this hasn't been broken out, the import code is NOT FULLY UPDATED HERE.

Feed for group memberships, in activity streams format.

Shows a feed; has proper pagination; accepts activitystreams "join"
activities to start a new membership.

Made two new functions, Subscription::bySubscriber() and
Subscription::bySubscribed(), to get streams of Subscription objects.

Converted Profile::getSubscribers() and Profile::getSubscriptions() to
use these functions.

Big thanks to the folks at http://pecl.php.net/bugs/bug.php?id=16745 for the secret juju!
Classes were being torn down before session save handlers got called at the end of the request, which exploded with complaints about being unable to find various classes.
Registering a shutdown function lets us explicitly close out the session before everything gets torn down.

Big thanks to the folks at http://pecl.php.net/bugs/bug.php?id=16745 for the secret juju!
Classes were being torn down before session save handlers got called at the end of the request, which exploded with complaints about being unable to find various classes.
Registering a shutdown function lets us explicitly close out the session before everything gets torn down.