break up monolithic xmppdaemon into multiple queue handlers

break up monolithic xmppdaemon into multiple queue handlers

Eventually, the poor xmppdaemon has become overloaded with extra
tasks. So, I've broken it up. Now, we have 5 background scripts, and
more coming:

* xmppdaemon.php - handles incoming XMPP messages only.
* xmppqueuehandler.php - sends notices from the queue out through XMPP.
* smsqueuehandler.php - sends notices from the queue out over SMS
* ombqueuehandler.php - sends notices from the queue out over OMB
* xmppconfirmhandler.php - sends confirmation requests out over XMPP.

This is in addition to maildaemon.php, which takes incoming messages.

None of these are "true" daemons -- they don't daemonize themselves
automatically. Use nohup or another tool to background them. monit can
also be useful to keep them running.

At some point, these might become fork()'ing daemons, able to handle
more than one notice at a time. For now, I'm just running multiple
instances, hoping they don't interfere.

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