Corrade/Containers/StringStlView.h file new in Git master

STL std::string_view compatibility for Corrade::Containers::String and Corrade::Containers::StringView.

Including this header allows you to convert a Corrade::Containers::String / Corrade::Containers::StringView from and to a C++17 std::string_view. A separate Corrade/Containers/StringStl.h header provides compatibility with std::string. See String STL compatibility and StringView STL compatibility for more information.