set WA_NoSystemBackground flag and removed (useless) setting of WA_OpaquePaintEvent flag

svn path=/trunk/KDE/kdebase/workspace/; revision=1017186

clients/nitrogen/nitrogenbutton.cpp

@@ -50,7 +50,7 @@ namespace Nitrogen
     colorCacheInvalid_(true)
   {
     setAutoFillBackground(false);
-    setAttribute(Qt::WA_OpaquePaintEvent, false);
+    setAttribute(Qt::WA_NoSystemBackground);
     
     {
       unsigned int size( client_.configuration().buttonSize() );

clients/nitrogen/nitrogenclient.cpp

@@ -95,7 +95,6 @@ namespace Nitrogen
     
     KCommonDecoration::init();
     widget()->setAttribute(Qt::WA_NoSystemBackground );
-    widget()->setAttribute( Qt::WA_OpaquePaintEvent );
     widget()->setAutoFillBackground( false );
     initialized_ = true;