[BZ#635593] Newline differences should be displayed and highlighted

Submitted by Kai Willadsen

Description

See bug 602933.

The idea is that when a newline character is part of a difference (in particular unicode newlines) it would be useful to have some way of showing that the newline characters are different.

At the moment, Meld discards line ending information and considers all newline characters/sequences to be equal. However, we can keep it around with splitlines(). It's not entirely clear in which situations we should take into account newline differences.