Core: Modernize

modernize-use-auto
modernize-use-nullptr
modernize-use-override
modernize-use-using
modernize-use-default-member-init (partially)

Change-Id: Idf10d7ffb1d98a04edc09a25c35e4e9e3abe87b5
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/coreplugin/jsexpander.cpp

@@ -101,7 +101,7 @@ JsExpander::JsExpander()
 JsExpander::~JsExpander()
 {
     delete d;
-    d = 0;
+    d = nullptr;
 }
 
 } // namespace Core