[m-rev.] for post-commit review: improve doc of grade components

[Julien Fischer]

On Fri, 14 Jan 2022, Zoltan Somogyi wrote:

> diff --git a/doc/user_guide.texi b/doc/user_guide.texi
> index 81fc89e94..c6aac139c 100644
> --- a/doc/user_guide.texi
> +++ b/doc/user_guide.texi
> @@ -8254,6 +8267,10 @@ since calls to, and returns from, procedures must execute more code,
>  but it avoids imposing any limit on stack size
>  other than the size of available memory.
> 
> +When targeting languages other than C,
> +the stack is always managed by the implementation of the target language,
> +so for them, the @samp{.stseg} modifier is neither relevant nor supported.

Perhaps:

     When targeting high-level C or languages other than C ...

(I know the paragraphs before talk about low-level C, so maybe that's
enough?)

> +
>  @item debugging
>  The default is to generate executables that do not support debugging.
>  However, when generating low-level C code,

> @@ -8299,8 +8325,12 @@ the auto-configuration script,
>  but can be overridden if desired
>  with the environment variable @env{MERCURY_DEFAULT_GRADE}.
>  @vindex MERCURY_DEFAULT_GRADE
> -Depending on your particular installation,
> -only a subset of these possible grades will have been installed.
> +On any given particular installation,
> +the Mercury runtime system and Mercury standard library
> +will be installed in only a subset of the possible grades;
> +you can find out which grades these are
> +by invoking the Mercury compiler
> +with the @samp{--output-libgrades} option.

Discussed in the other thread.

The rest looks fine.

Julien.