bug#18085: libc locales moved to separate package

[Ludovic Courtès]

The ‘locales’ output of libc is huge, and contains way more locale data
than anyone needs.

We should follow roughly what other distros do, that is:

  • Provide just 1 or 2 locales by default, in the ‘locales’ output (say
    en_US.utf8 and en_US.iso88591).

  • Add a parametric package that builds the specified locales, which
    users can choose to install and add to their $LOCPATH.

The big ‘locale-archive’ will actually be ignored when $LOCPATH is set,
as per locale/findlocale.c:

  /* We really have to load some data.  First we try the archive,
     but only if there was no LOCPATH environment variable specified.  */
  if (__glibc_likely (locale_path == NULL))
    {
      struct __locale_data *data
        = _nl_load_locale_from_archive (category, name);

Ludo’.