mutt_FormatString() not multibyte-aware
mutt_FormatString() isn't multibyte-aware in several ways.
First, it doesn't support padding with multibyte-chars due to lines like
'ch = *src++' etc.
Second, padding doesn't work if the string contains multibyte characters
since the pad length seems to be calculated by going with bytes and not
character cells of the result.
I would like to fix it but don't know how since one of the mbyte
functions failed for we in always returning 1 for the width. Maybe we
could also convert to utf-8 first because it's so trivial to test for
continuations (as mutt IIRC does in other places already).
Should I file a bug report for this to have a discussion in the BTS or
is a real fix easy enough so I don't have to?