Build time config is not consistent with compile time config macros.

[Kohei Takahashi]

Some permissive compilers allow to use some of c++11 (or 14/1z/...) features as a extension: e.g. clang allows using of rvalue references in gnu++98 mode. In that case, build time config (i.e. cxx11_rvalue_references) tells yes but boost/config.hpp defines BOOST_NO_CXX11_RVALUE_REFERENCES and <utility> doesn't define std::move, std::forward, and so on. Thus, the regression tests that depending on macros will be issued and failure.

This is not only clang and rv-ref combination but also any other compiler and feature combinations: gcc allows lambda in gnu++98 mode but clang doesn't.

IMO, the build time config should be compliant compile time config than compiler error. Any thoughts?