Editor code: tidy up BOOLs,NULLs and overrides pt3.

A few 'typedefs' replaced by 'using's
This shouldn't have any functional changes at all, just c++17 modernization
It's a part 3 of a split #2847

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

Code/Editor/TrackView/TrackViewDialog.h

@@ -52,7 +52,7 @@ class CTrackViewDialog
 public:
     friend CMovieCallback;
 
-    CTrackViewDialog(QWidget* pParent = NULL);
+    CTrackViewDialog(QWidget* pParent = nullptr);
     ~CTrackViewDialog();
 
     static void RegisterViewClass();
@@ -183,7 +183,7 @@ private:
     void OnAddEntityNodeMenu();
 
     void OnEditorNotifyEvent(EEditorNotifyEvent event) override;
-    BOOL OnInitDialog();
+    bool OnInitDialog();
 
     void SaveLayouts();
     void SaveMiscSettings() const;