[ubuntu] Accents stopped working with 16.04 in gedit

I upgraded from 15.10 to 16.04. Now the accents stopped working in some programs like gedit 3.18.3 but not in others like Firefox 46.0. In gedit, I type ' and then o wanting to get ó, but instead I get 'o separately. I have a keyboard: "Catalan (Spain, with middle-dot L)". In fact, it's an...