mod_muc_markers: Add option for @id rewriting, default off (may break some clients) XEP-0333 was updated to clarify that stanza-id should be used instead of the 'id' attribute when in a MUC. Some clients still use the id attribute, which is why we were rewriting it. Rewriting is bad because mod_muc advertises stable_id, indicating that Prosody does *not* rewrite ids. Recent versions of Conversations actually depend on this being true. All clients should migrate to using stanza-id for markers. See XEP-0333.

A module providing a streaming statistics interface like
[mod_statistics] but based on the new [statistics API][doc:statistics]
introduced in Prosody 0.10.

# Usage

To use, enable the built-in statistics like so:

```lua
statistics = "internal"
```

Then, in `modules_enabled`, replace `"statistics"` with
`"statistics_statsman"` and the various `"statistics_<something>"`
with equivalent `"measure_<something>"`.