Incidence::operator== didn't worlk properly when there were attachments involved.
Fixed by implementing ListBase::operator== and Attachment::operator==.
Review: http://reviewboard.kde.org/r/821/
This was also one of the causes of bug 195734.
BUG: 195734
MERGE: e4
svn path=/trunk/KDE/kdepimlibs/; revision=981640