Do not use QAbstractItemModel::reset().

Change-Id: Ie49bdf576a6d3543aef6df133b27c8827775c935
Rationale:
    a) It is conceptually cleaner to do the changes to the model
       in between calls to beginResetModel() and endResetModel,
       respectively.
    b) The function is deprecated in Qt 5, for exactly that reason.
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/debugger/breakhandler.cpp

@@ -1163,18 +1163,20 @@ void BreakHandler::saveSessionData()
 
 void BreakHandler::loadSessionData()
 {
+    beginResetModel();
     m_storage.clear();
-    reset();
+    endResetModel();
     loadBreakpoints();
 }
 
 void BreakHandler::removeSessionData()
 {
+    beginResetModel();
     Iterator it = m_storage.begin(), et = m_storage.end();
     for ( ; it != et; ++it)
         it->destroyMarker();
     m_storage.clear();
-    reset();
+    endResetModel();
 }
 
 void BreakHandler::breakByFunction(const QString &functionName)