Support countries joining the Euro currency zone in the next few years. For
example, we should recognize PL_EURO and PL_PREEURO appropriately in the
For generating locale data from CLDR for POSIX-like systems, we will need to
generate @euro and @preeuro locales. If POSIX can fall back from a variant (like
pl_PL@preeuro to pl_PL), then only the one variant will be physically necessary
that contains the opposite of the currency data of the main country locale.