[texinfo.tex 2022-12-19.22]
Consider this input file
```
\input texinfo
·
@bye
```
(the character is U+00B7, MIDDLE DOT). Only pdfTeX produces this
character; both XeTeX and LuaTeX silently discard it.
If you replace '·' with, say, 'Æ' (U+00C6, LATIN CAPITAL LETTER AE),
both XeTeX and LuaTeX abort with
```
Runaway argument?
! Paragraph ended before @UTFviiiTwoOctets was complete.
<to be read again>
@par
```
If you replace it with 'ÿ' (U+00FF, LATIN SMALL LETTER Y WITH
DIAERESIS), you get
```
! Undefined control sequence.
l.3 ÿ
```
If you replace it with 'Ā' (U+0100, LATIN CAPITEL LETTER A MACRON),
you get a~log warning
```
Missing character: There is no Ā ("100) in font cmr10!
```
inspite of a proper `\DeclareUnicodeCharacter` line for this character
in `texinfo.tex`.
Ouch, ouch, ouch :-)
Werner
