2.0.15:

* g++ 3.2 (and Mac OS X g++ 3.3) build fix.
  (Paul Pogonyshev)
* Compose: Fix slot lifetime regression introduced in 
  2.0.9. (Philip Langdale)
* tests: Small ISO C++ correctness fix (Marek Rouchal)
* Don't specify unused function parameter names.
  (Andris Pavenis)