Add way to enable/disable module

[LinuxJedi]

Hi,

It appears the module implements some mutexes which will in-general reduce the performance of Nginx. I understand that these exist because the alternative would be an IPC interface to the workers for which there is no hook.

I recommend you add a way to turn this module on/off, maybe even dynamically, so that data is only captured and mutexes are used when data needs to be captured.

[erikdubbelboer]

I just pushed a version to this branch: a001bd9 that has this feature. Is this something that would work for you?

When the module is disabled the overhead for each request is only the additional handler call plus one atomic variable lookup.