Qt/EPG: use a qgraphicsitem_cast instead of dynamic_cast

(cherry picked from commit a8c86004499bed7014dfbdbe188a113759f7e340)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/qt4/components/epg/EPGView.cpp

@@ -60,11 +60,7 @@ void EPGView::setStartTime( const QDateTime& startTime )
 
     for ( int i = 0; i < itemList.count(); ++i )
     {
-#ifndef WIN32
-        EPGItem* item = dynamic_cast<EPGItem*>( itemList.at( i ) );
-#else
-        EPGItem *item = NULL;
-#endif
+        EPGItem* item = qgraphicsitem_cast<EPGItem*>( itemList.at( i ) );
         if ( !item ) continue;
         item->setStart( item->start().addSecs( diff ) );
     }
@@ -114,11 +110,7 @@ void EPGView::updateDuration()
 
     for ( int i = 0; i < list.count(); ++i )
     {
-#ifndef WIN32
-        EPGItem* item = dynamic_cast<EPGItem*>( list.at( i ) );
-#else
-        EPGItem *item = NULL;
-#endif
+        EPGItem* item = qgraphicsitem_cast<EPGItem*>( list.at( i ) );
         if ( !item ) continue;
         QDateTime itemEnd = item->start().addSecs( item->duration() );