Editor code: tidy up BOOLs,NULLs and overrides pt6.

A few 'typedefs' replaced by 'using's
This shouldn't have any functional changes at all, just c++17 modernization
It's a part 6 of a split #2847

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

Code/Editor/ResourceSelectorHost.cpp

@@ -101,7 +101,7 @@ public:
     }
 
 private:
-    typedef std::map<string, const SStaticResourceSelectorEntry*, stl::less_stricmp<string> > TTypeMap;
+    using TTypeMap = std::map<string, const SStaticResourceSelectorEntry *, stl::less_stricmp<string>>;
     TTypeMap m_typeMap;
 
     std::map<string, string> m_globallySelectedResources;