Missing a library for supporting localized strings

I'm missing a library here which provides support for string localization.

An application targeting non-expert users, and which displays or prints any sort of text - must do so in the user's language. And for that to happen, it must obtain a localized-and-formatted string in that language, given a proto-string, or a template, and the arguments to format (e.g. numbers, names and so on).

A venerable system for doing this is [GNU gettext](https://www.gnu.org/software/gettext/) - which is C-based. But - I would expect there should be a C++-based library for this functionality which could be considered "awesome" enough for this collection. Otherwise, perhaps a note suggesting someone write that awesome library? :-)

I don't have a specific candidate I can recommend, but I have noticed [`spirit-po`](https://github.com/cbeck88/spirit-po), which is in C++ and reads GNU gettext `.po` files; haven't ever used it myself.