Make sure languages "with two parts" are handled correctly

[elegaanz]

For instance en-US or pt-BR

[trinity-1686a]

I think they should be because of https://github.com/Plume-org/rocket_i18n/blob/master/src/with_rocket.rs#L24 and https://github.com/Plume-org/rocket_i18n/blob/master/src/with_actix.rs#L50 ? Or did you mean somewhere else?

[elegaanz]

Yes, but my concern was more about making sure they are working with gettext-macros too, and that the two-parts version is correctly used when needed if the one-part version is also available (not sure if I'm clear, sorry).

[Valodim]

If I'm reading that code right, the locale part (so -Lo out of ln-Lo) is simply ignored?

I believe it is very important to support this because of the Chinese language. The locales "Chinese (Traditional)" and "Chinese (Simplified)" are quite different, but share the zh language prefix.