[Bug c++/52801] improve selective typedef unwrapping

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52801

--- Comment #2 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Eric Gallager from comment #1)
> Confirmed that the notes could ease up on the template spew; g++ output is
> now:

Note that I'm not complaining about the redundant notes listing the declaration
of the candidates (which are the subject of a different PR that I cannot find
right now). 

The object of improvement here is:

no known conversion from 'vector<Real>' to 'const std::basic_string<char>'

versus

no known conversion for argument 1 from ‘std::vector<double>’ to ‘const
std::__cxx11::basic_string<char>&’

On the latter, gcc is excessively unwrapping typedef.