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/TrackViewAnimNode.cpp

@@ -370,7 +370,7 @@ bool CTrackViewAnimNode::IsBoundToEditorObjects() const
         else
         {
             // check if bound to legacy entity
-            return (m_animNode->GetNodeOwner() != NULL);
+            return (m_animNode->GetNodeOwner() != nullptr);
         }
     }
 
@@ -1468,7 +1468,7 @@ bool CTrackViewAnimNode::PasteNodesFromClipboard(QWidget* context)
     }
 
     XmlNodeRef animNodesRoot = clipboard.Get();
-    if (animNodesRoot == NULL || strcmp(animNodesRoot->getTag(), "CopyAnimNodesRoot") != 0)
+    if (animNodesRoot == nullptr || strcmp(animNodesRoot->getTag(), "CopyAnimNodesRoot") != 0)
     {
         return false;
     }