patch: psql - enforce constant width of last column

Hi

When I played with vertical cursor support I got badly displayed last
columns when border was not 2. Only when border is 2, then psql displays
last column with same width for each row.

I think so we can force column width alignment for any border styles today
(for alignment and wrapping styles) or as minimum this behave can be
optional.

I wrote a patch with pset option "final_spaces", but I don't see a reason
why we trim rows today.

Regards

Pavel