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, 1 insertions, 1 deletions

diff --git a/mappingtablewidget.cpp b/mappingtablewidget.cpp
index d42fcb9..db5bbe3 100644
--- a/mappingtablewidget.cpp
+++ b/mappingtablewidget.cpp
@@ -115,7 +115,7 @@ void MappingTableWidget::removeItem(){
 	if(selected.isEmpty()){
 		return;
 	}
-    for(QPersistentModelIndex i : selected){
+    for(const auto &i : selected){
 		QString item = i.data().toString();
 		mModel->removeRows(i.row(), 1);
 		QModelIndex itemIdx = mMappingModel->find(item);