mod_bookmarks2: Add new module. This is the result of hacking during the Stockholm XMPP Sprint, for compatibility with older clients only doing Private XML XEP-0048. This module shouldn’t be loaded at the same time as mod_bookmarks, as both implement Private XML to achieve their conversion.

This module discards typing notifications sent to a bare host JID,
preventing error replies to be sent. These errors are harmless but can
be annoying sometimes if your client shows them prominently.