mod_measure_process: Report the enforced limit The soft limit is what the kernel actually enforces, while the hard limit is is how far you can change the soft limit without privileges. Unless the process dynamically adjusts the soft limit, knowing the hard limit is not as useful as knowing the soft limit. Reporting the soft limit and the number of in-use FDs allows placing alerts on expressions like 'process_open_fds / process_max_fds >= 0.95'

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.