mod_http_muc_log: Correctly handle changed or retracted reactions Since per XEP-0444 each reaction should overwrite all previous reactions on a particular message from a particular occupant. Previously repeated reactions would be counted again and retractions were not handled.

This module produces more detailed HTTP logs for Prosodys built-in HTTP
server. The format is similar to that of Apache and go into Prosodys
normal logs at the `info` level.