Fixed ambiguous CTADs.
Added new macro BOOST_HAS_CTAD_SFINAE to indicate that compiler supports SFINAE to disambiguate CTADs.
The macro BOOST_HAS_CTAD_SFINAE is currently undefined for all compilers (new versions of gcc may support it, cf. https://github.com/boostorg/container/issues/80, but I cannot check it)
Fixed ambiguous CTADs. Added new macro BOOST_HAS_CTAD_SFINAE to indicate that compiler supports SFINAE to disambiguate CTADs. The macro BOOST_HAS_CTAD_SFINAE is currently undefined for all compilers (new versions of gcc may support it, cf. https://github.com/boostorg/container/issues/80, but I cannot check it)