Re: what should install-world do when docs are not available?

> +        Enables the building of documentation in <acronym>HTML</acronym> and
> +        <acronym>man</acronym> format. It defaults to auto.
> +
> +        Enables the building of documentation in <acronym>PDF</acronym>
> +        format. It defaults to auto.

These sound awkward.  Recommend:

Enables building the documentation in <acronym>PDF</acronym>
format. It defaults to auto.

> +     <varlistentry id="configure-docs-html-style">
> +      <term><option>-Ddocs_html_style={ simple | website }</option></term>
> +      <listitem>
> +        <para>
> +         Influences which <acronym>CSS</acronym> stylesheet is used. If
> +         <literal>website</literal>, instead of the default
> +         <literal>simple</literal>, is used, HTML documentation will use the
> +         stylesheet used on <ulink
> +         url="https://www.postgresql.org/docs/current/">postgresql.org</ulink>.

s/Influences/Controls/

I think the default should be given separately from the description of
the other option.

Controls which <acronym>CSS</acronym> stylesheet is used.
The default is <literal>simple</literal>.
If set to <literal>website</literal>, the HTML documentation will use the
same stylesheet used on <ulink
url="https://www.postgresql.org/docs/current/">postgresql.org</ulink>.