mod_http_oauth2: Make note about handling repeated RFC 6749 states > If an authorization code is used more than once, the authorization > server MUST deny the request and SHOULD revoke (when possible) all > tokens previously issued based on that authorization code. We should follow the SHOULD. The MUST is already covered by removing the code state from the cache.

This module logs events where more than a certain amount of CPU time was
spent.

``` lua
log_cpu_threshold = 0.01 -- in seconds, so this is 10 milliseconds
```

Uses the Lua
[`os.clock()`](http://www.lua.org/manual/5.2/manual.html#pdf-os.clock)
function to estimate CPU usage.