Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

Phoenix now has a lazy list implementation which is very similar but not identical to the implementation provided by FC++.
- Details can be found in Lazy List.
- Tests have been added for the new features provided.
- This is an addition which causes no changes to the previous public interface.
Fixes for #10927 and #11085