Start of new ANTLR4 based parser.

Very simple tests pass.

pglablib/sqlparser/Parser.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include ".generated/PgsqlLexer.h"
+#include ".generated/PgsqlParser.h"
+#include "CaseChangingCharStream.h"
+#include "ErrorListener.h"
+
+class Parser
+{
+public:
+    Parser(const std::string &input_string);
+
+    std::unique_ptr<sqlast::StatementList> Parse();
+
+    int errorCount() const
+    {
+        return Errors.errorCount();
+    }
+private:
+    std::unique_ptr<antlr4::CharStream> InputStream;
+    CaseChangingCharStream CaseFilter;
+    PgsqlLexer Lexer;
+    antlr4::CommonTokenStream TokenStream;
+    PgsqlParser AParser;
+    ErrorListener Errors;
+};
+