Start of new ANTLR4 based parser.

Very simple tests pass.

pglablib/sqlast/SelectList.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include "Node.h"
+#include <memory>
+#include <vector>
+
+namespace sqlast {
+
+    class SelectItem;
+
+    class SelectList : public Node
+    {
+    public:
+        SelectList();
+
+        void Add(std::unique_ptr<SelectItem> select_item);
+        int Count() const;
+
+        SelectItem& Get(int index)
+        {
+            return *list.at(index);
+        }
+    private:
+        using List = std::vector<std::unique_ptr<SelectItem>>;
+
+        List list;
+    };
+
+}