add_info was a thing that grew organically to account for hidden
contras, but just wasn't right. The assumption was that if the
contra account is hidden, the contra itself should be hidden from
view - the sign of the amount would be wrong anyway.
The correct approach, however, would of course to flip the sign so it
matches the user's perspective, and to add a separate description string
to display to the user.
Beginning of a line was already trimmed, courtesy of the whitespace
split. The end of a line was previously not trimmed because of the limit
for split.
The signatures feature has been "experimental" since Perl 5.20 (May 2014), but
expected to stay. After 8 years I'm ready to take the risk :)
Have added Perl v5.28 (June 2018) as the minimum requirement, even though the
current revbank should work with 5.20, to see if this bothers any users. Perl
v5.28 is in Debian "buster", which is now oldstable.
