[Fontinst] wrong mappings in 'ot1tt'?

[Werner LEMBERG]

It's nice to wake up a dormant mailing list after more than six
years :-)  Hopefully, the relevant people are still listening...

In fontinst's file `ot1.etx` I can find the following mappings:

```
\setslot{circumflex}
   \comment{The circumflex accent `\^ a'.}
\endsetslot

\setslot{tilde}
   \comment{The tilde accent `\~a'.}
\endsetslot
```

I think this is wrong, at least for 'cmtt' and friends.  Today, the
most important use for glyph names is cut-and-paste support via the
`toUnicode` table – TeX and LaTeX themselves actually don't need glyph
names at all.

In the Adobe Glyph List (AGL,
https://github.com/adobe-type-tools/agl-aglfn), which is the de-facto
standard, 'circumflex' and 'tilde' are mapped to Unicode values U+02C6
and U+02DC, respectively.  However, I dare to say that whenever you
see a circumflex or tilde in a PDF document and you copy and paste it,
you want to get back the corresponding ASCII input characters.

As a corollary, I suggest to change the mapping values to
'asciicircum' and 'asciitilde'.  In case fonts don't provide such
glyph names (I haven't checked CM fonts), it would be the necessary to
adapt the font's MTX file accordingly.

In case you are curious: For LilyPond's documentation (which uses
Texinfo), we replace CM typewriter fonts with Latin Modern's
equivalents to also get bold and bold italic variants, allowing nice
B/W source code highlighting via Pygments.  To do so it was necessary
to create OT1-encoded metric files...

  https://gitlab.com/lilypond/lilypond/-/blob/master/Documentation/tex/lm-ot1.tex
  https://gitlab.com/lilypond/lilypond/-/blob/master/Documentation/tex/lm-ot1-map.tex

My patch to fix the abovementioned issue is

  https://gitlab.com/lilypond/lilypond/-/merge_requests/1699


    Werner