QmlJS: Improve handling of user defined enums

Improves handling of Qml based enums inside qml documents.

 * completion of enums
 * follow the enum
 * highlighting values inside the declaration
 * displaying the enum declaration inside the outline
 * minor static checks

Task-number: QTCREATORBUG-19226
Change-Id: Ia07fd9a8b7fa3106f2ea53198bfdcc50eecb7307
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

src/plugins/qmljseditor/qmljssemantichighlighter.cpp

@@ -348,6 +348,13 @@ protected:
         return visit(static_cast<FunctionExpression *>(ast));
     }
 
+    bool visit(UiEnumMemberList *ast) override
+    {
+        for (auto it = ast; it; it = it->next)
+            addUse(it->memberToken, SemanticHighlighter::FieldType);
+        return true;
+    }
+
     bool visit(PatternElement *ast) override
     {
         if (ast->isVariableDeclaration())