support lib utf8 strings in container

[timosachsenberg]

would reduce number of decodes from byte strings e.g. if a class returns a std::vectorstd::string -> [string1, string2]

[jpfeuffer]

Why is it not supported? What did you try?

[timosachsenberg]

Think I just forgot the utf8 libcpp_vector[libcpp_string] ... will check