CONCURRENT_DEBUG default state - active or not?

lib/modules/Concurrent.pmod starts out by defining CONCURRENT_DEBUG to the value 0. This counts as defined, for the purposes of storing backtraces and such. Is that meant to be active by default?

At the moment, there are a number of werror lines that are quite noisy; not sure whether they're part of current debugging efforts or if they're meant to be able to be controlled in that way. I added #ifdef guards, but since the file defines it initially, they're still showing up. For normal code, it would probably be better to not have the noisy output, but maybe it's best to hang onto the backtraces?

I believe this applies equally to master and 8.0.

ChrisA