Code review comment for lp:~vila/bzr/353370-notty-no-term-width

I wonder if we actually need two concepts here: the 'align right' width, and the 'truncation' width. So on an infinitely wide terminal, or when the terminal size is not known, you might assume 80 (or 132 or something) for the first, and not truncate at all. And there's also the question of the progress bar and other possible future things where we try to erase the whole contents of a line.

The bugs this touches are

https://bugs.edge.launchpad.net/bzr/+bug/62539 - trivial 'missing TIOCGWINSZ' "John A Meinel wrote on 2006-10-24: missed 0.12, is simple enough to happen soon." :-) Not controversial.

https://bugs.edge.launchpad.net/bzr-pager/+bug/353370 - assuming that non-ttys have 80 char width causes problems when bzr is run through a pager

https://bugs.edge.launchpad.net/bzr/+bug/458743 (now a dupe) - if Bazaar pretends the terminal is very wide for the sake of truncation, then it draws unreasonably wide progress bars.