Make it run with Qt6

This is a huge commit. Changes:
* Obviously, make it compile
* Make it run (only scarcely tested)
* get rid of most of clang's warnings

Let's see what surprises are in store...

1 files changed, 2 insertions, 2 deletions

diff --git a/mappingtreeresultmodel.cpp b/mappingtreeresultmodel.cpp
index e2ff75e..cb8d67c 100644
--- a/mappingtreeresultmodel.cpp
+++ b/mappingtreeresultmodel.cpp
@@ -112,7 +112,7 @@ void MappingTreeResultModel::removeItem(const QModelIndex &idx){
         return;
     }
     SmTreeItem *curItem = static_cast<SmTreeItem*>(idx.internalPointer());
-    MappingData rmData = mSourceModel->mappingDataFromItem(curItem);
+    const MappingData rmData = mSourceModel->mappingDataFromItem(curItem);
     beginResetModel();
     int row = curItem->row();
     SmTreeItem *parent = curItem->parent();
@@ -173,7 +173,7 @@ QList<QVariant> MappingTreeResultModel::columnValuesRecursive(SmTreeItem *parent
     for(int i = 0; i < parent->childCount(); ++i){
         SmTreeItem *child = parent->child(i);
         QVariant value = child->data(column);
-        if(value.canConvert(QVariant::Int) && (value.toInt() != -1)){
+        if(value.canConvert<int>() && (value.toInt() != -1)){
             retval << value;
         }
         retval << columnValuesRecursive(child, column);