[bug-mailutils] Not one single debugging example

[積丹尼 Dan Jacobson]

No matter (info "(mailutils) debugging") nor man mail,
there is not one single example to get the user started.

Sure, there is tons of documentation. But not one single example.

So, after

       --debug-level=LEVEL
              set Mailutils debugging level

please add:

Example:
       --debug-level=ALL (?)

Turn on all debugging output.

At least tell the user how to turn on ALL. Thanks.