Detailed Description
This was top level widget. It inherits KTMainWindow completely now.
You can still use is under this name, if you are so nostalgic.
You shouldn't use this widget it might be removed from libraries
in future.
The only difference is that KTMainWindow is per default created with
the WDestructiveClose flag. This means, it is automatically
deleted when the widget accepts a close event. A KTopLevelWidget
needs to be deleted manually ( it is basically a just a KTMainWindow( "name", 0 ); )