mod_sasl2_fast: Fix harmless off-by-one error (invalidates existing tokens!) Problem: This was causing the key to become "<token>--cur" instead of the expected "<token>-cur". As the same key was used by the code to both set and get, it still worked. Rationale for change: Although it worked, it's unintended, inconsistent and messy. It increases the chances of future bugs due to the unexpected format. Side-effects of change: Existing '--cur' entries will not be checked after this change, and therefore existing FAST clients will fail to authenticate until they attempt password auth and obtain a new FAST token. Existing '--cur' entries in storage will not be cleaned up by this commit, but this is considered a minor issue, and okay for the relatively few FAST deployments.

This module compares the memory usage reported by Lua before and after
each event and reports it to the log if it exceeds the configuration
setting `log_memory_threshold` (in bytes).

``` lua
log_memory_threshold = 20*1024
```

If you are looking to identify memory leaks, please first read [Three
kinds of memory
leaks](https://blog.nelhage.com/post/three-kinds-of-leaks/).

Prosody runs on Lua which uses automatic memory management with garbage
collection, so the numbers reported by this module are very likely to be
useless for the purpose of identifying memory leaks. Large, but
temporary, increases in memory usage can however highlight other kinds
of performance problems and sometimes even provide hits for where to
look for memory leaks.