whish config_charset feature enhancements

[Alain Bench <veronatif@…>]

    That was already posted to mutt-dev in early 2004, but after recent closure of mutt/1642 I repeat for the record:

 1) The doc should state that a sourced muttrc is recoded from $config_charset *to $charset*. And this implies $charset has to be set early enough in muttrc. This is especially important for people with -HAVE_LANGINFO_CODESET, and people playing with //TRANSLITerations.

 2) Users should be warned that recoding to a poorer charset can change chars to question marks, possibly breaking regexps and such.

 3) //TRANSLIT users should be warned that this can insert spurious quotes, double quotes, backtics and such, possibly breaking muttrc syntax.

 4) Reverse recoding from $charset to $config_charset could be done when saving a new alias to $alias_file thru <create-alias>.

 5) Recoding of $signature file could be done.

 6) Read/write recoding of $history_file could be done (see the excellent patch-1.5.1.vl.savehist.1 from Vincent Lefèvre).
>How-To-Repeat:
>Fix:
Unknown

[Rocco Rutte <pdmef@…>]

(In [15d93fe50e62]) Clarify documentation for $config_charset. Closes #2021.

[pdmef]

For the record:

1. done
2. done
3. I think people adding //TRANSLIT manually should be aware of this. This is noise for the majority of users I guess.
4. Fixed in [f93dcd689032]
5. $signature is not really a configuration file.
6. history files are written/read in utf-8, no need for $config_charset (because it's supposed to be completely maintained by mutt)