2.11: Improved highlighting

This release properly highlights the following kinds of changes:

- Some lines changed, plus extra lines added at the end
- Some lines changed, plus extra lines added at the beginning
- Some lines changed, plus some lines removed at the end
- Some lines changed, plus some lines removed at the beginning

For example, this means that if you have a multi line list in your source code,
and add a comma to one line, plus a number of more lines after that, the comma
will now be highlighted.

Highlighting the rest of those lines doesn't provide value since they are all
new, which should be obvious anyway.