bug#39215: Hyperlinks to man pages in doc strings

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Tue, 21 Jan 2020 09:55:42 +0100
> 
> Severity: wishlist
> 
> Please add the possibility to write in doc strings:
> 
>     man page `find'
> 
> and have it automatically converted into a hyperlink which will open
> up M-x man and visit the specified man page.

'find' has an Info manual: find.info.  Why not use a hyperlink to that
instead, something we already support?  Many utilities have similar
Info manuals, and the glibc has an Info manual as well.

> The proposed feature complements the already existing functionality
> with hyperlinks to info pages.[1]

Nitpicking: let's not call Info manuals "pages".  They are not like
"man pages", which are a collection of short concise usage
descriptions.