locale fallback option

[Wermut <wermut@gmail.com>]

Hi

I just read, that you committed the basic locale code and about the
musl firsts and thought of one thing that I would really like to see
in a modern implementation.

Problem: User A speaks a language "xyz" and lives in country "AB". So
he will set the relevant locale environment vars to "xyz_AB". The
problem is, that the language "xyz" is only spoken by a minority of
people and the translation of the software in his language is often
not complete or non existend. The result is, that user A will have to
read the most strings in plain english, because this is the standard
fallback. Because our user A is a member of a minority, he knows also
the language "ts" which is also spoken in "AB", but he does not know
any english.

Status quo: Because the translation "xyz_AB" is not really complete,
the user A gives up, is frustrated and sets his locale to "ts_AB".

What really should be possible: User A sets the locale "xyz_AB" and
sets "ts_AB" as a fallback for definitions and strings not available
in "xyz_AB". Only if a string is not defined in either "xyz_AB" or
"ts_AB", the hardcoded english string is shown to him.

This would require, that the locale definition would accept something
like LANG=xyz_AB:ts_AB

I have worked in the past with some of these translation problems and
worked with people from a lot of minorities that have all the same
problem: The locale subsystem is just no flexible enough. I know that
the implementation is potentially expensive, because you could end up
in looking into a lot of physical files on your hard drive, but it
would definitive be a big improvement and would help that almost
distinguished language would be used more often in computer
translations.

Thanks for reading.

Regards

Kevin