A massive amount of doinking around in <string>.
https://cplusplus.github.io/LWG/issue2946 https://cplusplus.github.io/LWG/issue3075 https://cplusplus.github.io/LWG/issue3076
This is not quite right yet, but I wanted to get it up here for people to look at.
I may have stepped on a bug fix for old versions of gcc in C++03 mode - Eric? [ was introduced in r292830 ]
Stephan - I updated your deduction guide tests now that we implement all of them.