refactoring qad widgets part 2

c++ cast, nullptr, forward declaration, agregate ui, connect to member functions, order and clear includes

libs/widgets/qcodeedit_completer_p.cpp

@@ -1,5 +1,6 @@
 #include "qcodeedit_completer_p.h"
 #include "qad_types.h"
+#include <QKeyEvent>
 #include <QHeaderView>
 
 
@@ -22,7 +23,6 @@ QCodeEditCompleter::QCodeEditCompleter(QWidget * parent): QTreeWidget(parent) {
 #endif
 				(QHeaderView::ResizeToContents);
 	header()->setStretchLastSection(false);
-	//connect(verticalScrollBar(), SIGNAL(valueChanged(int)), this, SLOT(adjust()));
 }