Since the last kdelibs snapshot, KAction is now derived from the new
QWidgetAction. I've been waiting for this change because it allows me
to place text labels in the popup menu properly without having the
greyed-out tex of disabled menu items.

The object-data portion of the KSPopupMenu is now composed of QLabels
with boldface, centered text.

I also removed '#include "kspopupmenu.h"' from skyobject.h, so changing
the popup menu won't require recompiling most of the program! To do
this, I just had to move SkyObject::showPopupMenu() from an inline
function to the skyobject.cpp source code file.