Re: `@findex` within paragraph doesn't work

[Werner LEMBERG]

>> > This was a deliberate change to make index commands terminate
>> > paragraphs.
>> 
>> Well, it stayed completely undocumented...
> 
> It is in NEWS, but not in a released version admittedly.

OK, but there isn't a single word in the Texinfo manual that index
commands now automatically end a paragraph if not immediately preceded
by `@item`.

> I looked at where this was used in the manual in question and it
> wasn't obvious that the index entries were in the right place as all
> the "Predefined commands" section was a list of commands but no
> explanation of those commands.

Yes, a list, but neither `@itemize` nor `@enumerate` but just a simple
paragraph.

> I can't think of a way right now of supporting this with the current
> approach.  [...]

What about introducing a new flag, something like

```
@set txiindexinpara
```

that restores the previous behaviour?  At least on the `texinfo.tex`
side this shouldn't be too difficult.  However, I have no idea about
`makeinfo` and `texi2any`...

Currently, there are more than 28500 index entries in the LilyPond
manuals (counting all translations), which really means *a lot* of
work of checking and reordering before being able to update to a more
recent `texinfo.tex`.  Hopefully, I can find a good regex for
`pcregrep` to simplify at least the checking.

This backward-incompatible change IMHO needs a *much* bigger
warning in the NEWS file, and it needs real documentation too, as
mentioned above.


    Werner