normalization problem with `@anchor` targets

[Werner LEMBERG]

[texinfo.tex 2025-02-03.17]
[texi2any 7.2]

Consider the following input file `bogen.texinfo`.  The German word
'Bögen' is the plural of 'Bogen' – in music, this is 'slur'
vs. 'slurs'.

```
\input texinfo

@node Top
@top Top
top

@node Foo
@chapter Foo

@anchor{Bogen}Bogen

@page

@node Bar
@chapter Bar

@anchor{Bögen}Bögen

@page

@node Baz
@chapter Baz

reference to Bogen: @ref{Bogen}

reference to Bögen: @ref{Bögen}

@bye
```

Processing with `texi2pdf` gives a warning:

```
pdfTeX warning (ext4): destination with the same identifier (name{Bogen}) has b
een already used, duplicate ignored
<to be read again> 
                   @penalty 
@safewhatsit ...um @whatsitpenalty >9999 @penalty 
                                                  @whatsitpenalty @fi @else ...

@setref #1#2->@pdfmkdest {#1}
                             @iflinks {@requireauxfile @atdummies @def @valu...

@@anchor:impl #1->@savesf @setref {#1}{Yanchor}
                                               @restoresf @ignorespaces 
l.17 @anchor{Bögen}
```

In the PDF, the reference to 'Bögen' is the same as with 'Bogen'.

Processing this with `texi2any --html` yields a warning, too:

```
bogen.texinfo:17: warning: @anchor `Bögen' file Bogen.html for redirection 
exists
bogen.texinfo:10: warning: conflict with @anchor `Bogen' redirection file
```

And indeed, a redirection file for 'Bögen' is missing, AFAICS.

So: Why does 'Bögen' gets normalized to 'Bogen' for anchors,
apparently in both `texinfo.tex` and `texi2any`?


    Werner