Open gedit, type in "wouldn't" without the quotes, and either enable Autocheck
spelling (Tools menu) or use Check Spelling to open the dialogue. Gedit suggests
replacing the "wouldn" part with "wouldn't", which is performed, would yield
"wouldn't't". Also works with "doesn't", "couldn't", "shouldn't" etc. and
anything where the contracted form adds letters to the original word, i.e.
"should not" becomes "shouldn't". Obviously "shouldn" isn't a word... but you
know what I'm getting at :) Apostrophes seem to be considered as the end of a
word, like whitespace.
$ dpkg -l | grep gedit
ii gedit 2.12.0-0ubuntu1 light-weight text editor
ii gedit-common 2.12.0-0ubuntu1 light-weight text editor support files