mod_firewall: spam-blocking.pfw: Remove requirement for invites to have no body Some clients (e.g. Gajim) send a body, which I guess makes sense. The bare JID sender check should already make it hard to bypass this (i.e. a normal client putting muc#user into a normal chat message shouldn't bypass the usual message filters).

This module writes out a traceback to `traceback.txt` in Prosodys data
directory (see `prosodyctl about`) when the signal `SIGUSR1` is
received. This is useful when debugging seemingly frozen instances in
case it is stuck in Lua code.