Comment 3 for bug 1898902

In the section for LC_NUMERIC, locale(5) says:

  decimal_point
    followed by the string that will be used as the decimal delim-
    iter when formatting numeric quantities.

.. without constraint on what the string may include. It appears this is actually constrained by processors to be a single character, as at https://code.woboq.org/userspace/glibc/locale/programs/ld-numeric.c.html#229

It is not clear if that is part of the spec: if so, I think this should be made explicit in the man page; if not, it is probably still worth noting that some applications (such as localedef) require it.

I have not checked, but it seems likely that thousands_sep has the same constraint, and would need similar treatment.

Initially reported for Ubuntu at https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/1898902, they recommended I re-post upstream.