mod_adhoc_dataforms_demo: Fix duplicate field prevention It's supposed to only include each type of form field once per form at most but it didn't note which fields it had added already. No idea what the probability was anyways, probably pretty low.

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.