Inconsistency between tr and cut on multibyte character

Hi,

I downloaded the last release and have a strange behaviour.

I have the following test.txt file (utf8 encoded)

zone1§zone2§zone3

$ ./coreutils cut -d§ -f2 test.txt
zone2
$ cat test.txt | ./coreutils tr '§' ';'
zone1;;zone2;;zone3

the cut command behave as I would expect (although the output is different from the gnu cut)
However, tr should not double ;

Basically, it seems to work fine when tr replace n byte(s) character by another n byte(s) character, but is broken if I try to replace a n byte(s) character by a m byte(s) character.

Start by reproducing the reported behavior through the tr command entry point with the UTF-8 test.txt content containing §, then compare its output with cut and the expected single-character replacement. The issue is done when replacing the multibyte character with ; produces one ; per occurrence rather than duplicates, with the behavior covered by a regression test if the relevant test location is found.