Start of new ANTLR4 based parser.

Very simple tests pass.

pglablib/sqlast/StringLiteral.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "Literal.h"
+#include <QString>
+#include <string>
+
+namespace sqlast {
+
+    class StringLiteral : public Literal
+    {
+    public:
+        explicit StringLiteral(const std::string s);
+
+        QString GetValue() const { return value; }
+    private:
+        QString value;
+    };
+
+}