[gedit-list] gedit doesn't handle apostrophes correctly when spell-checking

[Ma Xiaojun <damage3025 gmail com>]

The title is borrowed from:
http://pad.lv/36227

To reproduce:
1. Type "Gedit isn't smart." into an empty buffer.
2. Tools => Check Spelling
3. It reports that "Gedit" and "isn" is misspelled.

There is a bug reported in 2004:
https://bugzilla.gnome.org/show_bug.cgi?id=131576