Editor code: tidy up BOOLs,NULLs and overrides pt2.

A few 'typedefs' replaced by 'using's
This shouldn't have any functional changes at all, just c++17 modernization
It's a part 2 of a split #2847

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

Code/Editor/Objects/TrackGizmo.cpp

@@ -34,7 +34,7 @@ namespace {
 //////////////////////////////////////////////////////////////////////////
 CTrackGizmo::CTrackGizmo()
 {
-    m_pAnimNode = 0;
+    m_pAnimNode = nullptr;
 
     m_worldBbox.min = Vec3(-10000, -10000, -10000);
     m_worldBbox.max = Vec3(10000, 10000, 10000);