Squish: Fix tst_session_handling

Change-Id: I85348bffe6c24be4663f67fc62e95a3e663b828c
Reviewed-by: Robert Loehning <robert.loehning@digia.com>
Refactor internal structures inside diff editor

Move "changed" property out of TextLineData into
RowData as "equal".

Change-Id: Id9cb87d099cecb61a2774e7a4fffcc162dece604
Reviewed-by: Jarek Kobus <jaroslaw.kobus@digia.com>