Major refactoring of queue handlers to support running multiple sites in one daemon.

Key changes:
* Initialization code moved from common.php to StatusNet class;
  can now switch configurations during runtime.
* As a consequence, configuration files must now be idempotent...
  Be careful with constant, function or class definitions.
* Control structure for daemons/QueueManager/QueueHandler has been refactored;
  the run loop is now managed by IoMaster run via scripts/queuedaemon.php
  IoManager subclasses are woken to handle socket input or polling, and may
  cover multiple sites.
* Plugins can implement notice queue handlers more easily by registering a
  QueueHandler class; no more need to add a daemon.

The new QueueDaemon runs from scripts/queuedaemon.php:

* This replaces most of the old *handler.php scripts; they've been refactored
  to the bare handler classes.
* Spawns multiple child processes to spread load; defaults to CPU count on
  Linux and Mac OS X systems, or override with --threads=N
* When multithreaded, child processes are automatically respawned on failure.
* Threads gracefully shut down and restart when passing a soft memory limit
  (defaults to 90% of memory_limit), limiting damage from memory leaks.
* Support for UDP-based monitoring: http://www.gitorious.org/snqmon

Rough control flow diagram:
QueueDaemon -> IoMaster -> IoManager
                           QueueManager [listen or poll] -> QueueHandler
                           XmppManager [ping & keepalive]
                           XmppConfirmManager [poll updates]

Todo:

* Respawning features not currently available running single-threaded.
* When running single-site, configuration changes aren't picked up.
* New sites or config changes affecting queue subscriptions are not yet
  handled without a daemon restart.
* SNMP monitoring output to integrate with general tools (nagios, ganglia)
* Convert XMPP confirmation message sends to use stomp queue instead of polling
* Convert xmppdaemon.php to IoManager?
* Convert Twitter status, friends import polling daemons to IoManager
* Clean up some error reporting and failure modes
* May need to adjust queue priorities for best perf in backlog/flood cases

Detailed code history available in my daemon-work branch:
http://www.gitorious.org/~brion/statusnet/brion-fixes/commits/daemon-work

plugins/Facebook/facebookqueuehandler.php

@@ -1,4 +1,3 @@
-#!/usr/bin/env php
 <?php
 /*
  * StatusNet - the distributed open-source microblogging tool
@@ -18,21 +17,9 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-define('INSTALLDIR', realpath(dirname(__FILE__) . '/../..'));
+if (!defined('STATUSNET') && !defined('LACONICA')) { exit(1); }
 
-$shortoptions = 'i::';
-$longoptions = array('id::');
-
-$helptext = <<<END_OF_FACEBOOK_HELP
-Daemon script for pushing new notices to Facebook.
-
-    -i --id           Identity (default none)
-
-END_OF_FACEBOOK_HELP;
-
-require_once INSTALLDIR . '/scripts/commandline.inc';
 require_once INSTALLDIR . '/plugins/Facebook/facebookutil.php';
-require_once INSTALLDIR . '/lib/queuehandler.php';
 
 class FacebookQueueHandler extends QueueHandler
 {
@@ -41,33 +28,24 @@ class FacebookQueueHandler extends QueueHandler
         return 'facebook';
     }
 
-    function start()
+    function handle_notice($notice)
     {
-        $this->log(LOG_INFO, "INITIALIZE");
+        if ($this->_isLocal($notice)) {
+            return facebookBroadcastNotice($notice);
+        }
         return true;
     }
 
-    function handle_notice($notice)
+    /**
+     * Determine whether the notice was locally created
+     *
+     * @param Notice $notice the notice
+     *
+     * @return boolean locality
+     */
+    function _isLocal($notice)
     {
-        return facebookBroadcastNotice($notice);
+        return ($notice->is_local == Notice::LOCAL_PUBLIC ||
+                $notice->is_local == Notice::LOCAL_NONPUBLIC);
     }
-
-    function finish()
-    {
-    }
-
 }
-
-if (have_option('i')) {
-    $id = get_option_value('i');
-} else if (have_option('--id')) {
-    $id = get_option_value('--id');
-} else if (count($args) > 0) {
-    $id = $args[0];
-} else {
-    $id = null;
-}
-
-$handler = new FacebookQueueHandler($id);
-
-$handler->runOnce();