Treat spaces as ordinary characters in diff view

When showing a diff, spaces should be treated as ordinary text. I.e.
if spaces doesn't fit into the diff width, they should be moved to the
next line.

One example of an incorrect behavior: line ends with multiple spaces
and one space at the end of the line is removed. Without this fix,
the highlight for removed space always displays at the same line, where
the last text character is displayed. As a result, highlight can be
displayed on top of the right side instead of the left side.

Change-Id: I3fc9032052962d5a6c9036b68626f199677ec01d