Fix inventory overwrite

So I was wrong about curses having a truncation-friendly print method, so I just truncated the string manually.  Unfortunately this will not work with multibyte characters, need a dumb truncation method, the ones we have now are too smart and fold instead of truncating.  If they are multibyte it'll truncate a little early, which isn't the end of the world.
The underlying problem is the menu isn't split into separate windows, if it were I think It'd truncate automatically.
Candidate for 0.A
Easy reproduction is spawn contained non-drowsy cough syrup and look at your inventory as mentioned in #6358