Editor code: tidy up BOOLs,NULLs and overrides pt1.

A few 'typedefs' replaced by 'using's
This shouldn't have any functional changes at all, just c++17 modernization
It's a part 1 of a split #2847

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

Code/Editor/Controls/SplineCtrl.h

@@ -59,7 +59,7 @@ public:
     // Lock value of first and last key to be the same.
     void LockFirstAndLastKeys(bool bLock) { m_bLockFirstLastKey = bLock; }
 
-    void SetSpline(ISplineInterpolator* pSpline, BOOL bRedraw = FALSE);
+    void SetSpline(ISplineInterpolator* pSpline, bool bRedraw = false);
     ISplineInterpolator* GetSpline();
 
     void SetTimeMarker(float fTime);