Scan listings shall not contain body content. Hence, removed this feature.

Scan listings shall not contain body content. Hence, removed this feature.
Scan listings shall operator on message headers and non-message information
only. Displaying the beginning of the body complicates everything too much.
That's no surprise, because it's something completely different. If you
want to examine the body, then use show(1)/mhshow(1).
Changed the default scan formats accordingly.