Python should default to static linkage

https://github.com/boostorg/python/blob/d6d54ce483c27ef2cddb4d43e6e775c5c496ec62/include/boost/python/detail/config.hpp#L62

I think this would make boost-python more consistent with the rest of boost:
```cpp
- # elif !defined(BOOST_PYTHON_DYNAMIC_LIB)
+ # elif defined(BOOST_ALL_DYN_LINK) || defined(BOOST_PYTHON_DYN_LINK)
```

There was a thread about this back in 2008, but I didn't see any comments.
https://lists.boost.org/Archives/boost/2008/12/146488.php