ui/ncurses/text-screen: trim long lines

ui/ncurses/text-screen: trim long lines

When a text_screen is given a long line, it'll wrap to the next,
overstepping the left margin.

We already have folded text for flowed text screens, so just trim long
lines at the correct column.

This exposes an off-by-one with the automatic wrapping in
text_screen_set_text(), where we may overrun the last char, so fix that
too.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>