bug#50143: 28.0.50; Various issues with `tamil-itrans' input method

[Eli Zaretskii <eliz@gnu.org>]

> From: Visuwesh <visuweshm@gmail.com>
> Cc: 50143@debbugs.gnu.org,  rameshnedunchezian@outlook.com
> Date: Sun, 13 Mar 2022 11:29:53 +0530
> 
>     1. There's still a problem with tamil-itrans docstring.  It
>        currently leads the user into thinking that they can input the
>        Tamil digits.  The problem is that I am not sure how I can split
>        `quail-tamil-itrans-various-signs-and-digits-table' into two
>        cleanly.  Ideas are welcome.

I'd split into two parts the code that computes
quail-tamil-itrans-various-signs-and-digits-table, such that the Tamil
digits are in a separate part.  Then change the doc strings of the two
input methods so that the digits part is only included in the
documentation of the input method that supports their insertion.

>    2. The problem with the include variable syntax is because `quail-help'
>       (which is used eventually by `describe-input-method') calls
>       `substitute-command-keys' on the docstring so to get the intended
>       behaviour, one has to write \\=\\<VAR> not \\<VAR>.  The logic,
>       otherwise, is fine.  Maybe this needs to be documented?

Yes, please.

Thanks.