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/TimelineCtrl.cpp

@@ -58,7 +58,7 @@ TimelineWidget::TimelineWidget(QWidget* parent /* = nullptr */)
 
     m_bIgnoreSetTime = false;
 
-    m_pKeyTimeSet = 0;
+    m_pKeyTimeSet = nullptr;
 
     m_markerStyle = MARKER_STYLE_SECONDS;
     m_fps = 30.0f;