Enabled the use of Debugger-specific watch/locals models.

- Modified WatchModel to handle storage of an hierarchy
  of WatchItems.
- Factored out code for asynchronous population to
  AsyncWatchModel and added a mixin for convenient
  handling
- Added base class for synchronous models.
- Implement simple, synchronous models for CDB, greatly
  simplifying code and finally getting manual
  expansion right.
Signed-off-by: hjk <qtc-committer@nokia.com>

src/plugins/debugger/watchwindow.cpp

@@ -327,9 +327,11 @@ void WatchWindow::editItem(const QModelIndex &idx)
     Q_UNUSED(idx); // FIXME
 }
 
-void WatchWindow::setModel(QAbstractItemModel *model)
+void WatchWindow::setModel(QAbstractItemModel *newModel)
 {
-    QTreeView::setModel(model);
+    if (model() == newModel)
+        return;
+    QTreeView::setModel(newModel);
 
     setRootIsDecorated(true);
     header()->setDefaultAlignment(Qt::AlignLeft);
@@ -337,7 +339,7 @@ void WatchWindow::setModel(QAbstractItemModel *model)
     if (m_type != LocalsType)
         header()->hide();
 
-    connect(model, SIGNAL(layoutChanged()), this, SLOT(resetHelper()));
+    connect(newModel, SIGNAL(layoutChanged()), this, SLOT(resetHelper()));
 }
 
 void WatchWindow::resetHelper()