Add tests for threads/processes

[phoe]

I see no tests for threads/processes in the CCL test suite. It would be worthwhile to add those.

[Slids]

Heres a start:
#8

[kpoeck]

We could also use tests from the bordeaux-threads tests.
https://github.com/sionescu/bordeaux-threads/blob/master/test/bordeaux-threads-test.lisp