pytest.ini: Set a variable so module code can adapt to test runner
Over at https://github.com/coala/coala-quickstart/issues/295 , there are some problems running coala-quickstart using multiprocessing on Python 3.4, 3.5 and on Windows.
How badly these effect real use is not known.
However it is certain that removing profiling helps the Linux builds, but doesnt help the Windows builds.
Rather than disable multiprocessing in all scenarios, preventing any real testing, we need a flag which can be used to turn off multiprocessing in those specific scenarios only when running the test suite.
That allows the builds to pass again, and we can then start investigating solutions.