[B2] Propagate CXX requirements to consumers

From: Alexander Grund (alexander.grund_at_[hidden])
Date: 2020-05-15 17:00:29

Hello,

I'm trying to specify that my library uses C++11 (features) and cannot 
be compiled or used without.

Using `[ requires cxx11_defaulted_functions]` as the project 
"requirements" does work (lib not build), but e.g. the tests are still 
build and obviously failing.

Putting the above as "usage-requirements"Â  (just like 
`<link>shared:<define>BOOST_NOWIDE_DYN_LINK=1`) doesn't have any effect.

What is the proper way to do this?

Thanks,
Alex