Runtime threads, CMake, fixed warnings

[dorooleg]

1. Added ability to set threads in runtime
2. Using CMake for examples and tests
3. Fixed warnings for clang compiler

@dvyukov, what do you think is better to create a lot of little PR or use the current big?

[dvyukov]

Hi @dorooleg,

Thanks for improving things. There are quite a few patches to review at once. I also see some merges, which I prefer to be removed (let's keep history linear). Also I see a commit which conflicts with your recent commit that is already merged, this needs to be resolved.

Please split commits into logical smaller groups. Say, one can be fixing various compiler warnings and minor cleanups (which is always good). Then, then adding Makefiles. Let's do Makefiles instead of cmake, cmake is rather convoluted and obscure system.

What's the motivation for making thread counts dynamic? How does this affect performance?