Editor code: tidy up BOOLs,NULLs and overrides pt4.

A few 'typedefs' replaced by 'using's
This shouldn't have any functional changes at all, just c++17 modernization
It's a part 4 of a split #2847

Signed-off-by: Nemerle <nemerle5+git@gmail.com>

Code/Editor/Undo/Undo.cpp

@@ -34,7 +34,7 @@ public:
     {
         m_undoSteps.push_back(step);
     }
-    virtual int GetSize() const
+    int GetSize() const override
     {
         int size = 0;
         for (int i = 0; i < m_undoSteps.size(); i++)
@@ -43,18 +43,18 @@ public:
         }
         return size;
     }
-    virtual bool IsEmpty() const
+    bool IsEmpty() const override
     {
         return m_undoSteps.empty();
     }
-    virtual void Undo(bool bUndo)
+    void Undo(bool bUndo) override
     {
         for (int i = m_undoSteps.size() - 1; i >= 0; i--)
         {
             m_undoSteps[i]->Undo(bUndo);
         }
     }
-    virtual void Redo()
+    void Redo() override
     {
         for (int i = 0; i < m_undoSteps.size(); i++)
         {
@@ -113,8 +113,8 @@ CUndoManager::CUndoManager()
     m_bRecording = false;
     m_bSuperRecording = false;
 
-    m_currentUndo = 0;
-    m_superUndo = 0;
+    m_currentUndo = nullptr;
+    m_superUndo = nullptr;
     m_assetManagerUndoInterruptor = new AssetManagerUndoInterruptor();
 
     m_suspendCount = 0;
@@ -270,7 +270,7 @@ void CUndoManager::Accept(const QString& name)
     }
 
     m_bRecording = false;
-    m_currentUndo = 0;
+    m_currentUndo = nullptr;
 
     SignalNumUndoRedoToListeners();
 
@@ -303,7 +303,7 @@ void CUndoManager::Cancel()
     }
 
     delete m_currentUndo;
-    m_currentUndo = 0;
+    m_currentUndo = nullptr;
     //CLogFile::WriteLine( "<Undo> Cancel OK" );
 }
 
@@ -582,7 +582,7 @@ void CUndoManager::SuperAccept(const QString& name)
 
     //CLogFile::FormatLine( "Undo Object Accepted (Undo:%d,Redo:%d)",m_undoStack.size(),m_redoStack.size() );
     m_bSuperRecording = false;
-    m_superUndo = 0;
+    m_superUndo = nullptr;
     //CLogFile::WriteLine( "<Undo> SupperAccept OK" );
 
     SignalNumUndoRedoToListeners();
@@ -616,7 +616,7 @@ void CUndoManager::SuperCancel()
 
     m_bSuperRecording = false;
     delete m_superUndo;
-    m_superUndo = 0;
+    m_superUndo = nullptr;
     //CLogFile::WriteLine( "<Undo> SuperCancel OK" );
 }
 
@@ -708,8 +708,8 @@ void CUndoManager::Flush()
 
     delete m_superUndo;
     delete m_currentUndo;
-    m_superUndo = 0;
-    m_currentUndo = 0;
+    m_superUndo = nullptr;
+    m_currentUndo = nullptr;
 
     SignalUndoFlushedToListeners();
 }