to allow changing sidebar pages by keeping the left mouse
button pressed and moving the cursor over the icon list,
similar to a popup menu or the treelist version of the
tab bar in Konversation.

A remaining bug in the sidebar is that switching iconlist
items using the keyboard arrow keys won't switch sidebar
pages. I will fix that next time, unless someone else is
faster.

svn path=/trunk/KDE/kdegraphics/okular/; revision=1034540