Further improvements to spell checking support (issue #137).
- Add "Add to dictionary" context menu option.
- Use available translations for "Add to dictionary" and "No spelling suggestions".
- Fix placement of context menu separators.
- Display the "No spelling suggestions" option as grayed out.

git-svn-id: http://chromiumembedded.googlecode.com/svn/trunk/cef3@1879 5089003a-bbd8-11dd-ad1f-f1f9622dbc98