LibSQL: Move Lexer and Parser machinery to AST directory

The SQL engine is expected to be a fairly sizeable piece of software.
Therefore we're starting to restructure the codebase for growth.

Userland/Libraries/LibSQL/AST/SyntaxHighlighter.h

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2021, Dylan Katz <dykatz@uw.edu>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibSyntax/Highlighter.h>
+
+namespace SQL::AST {
+
+class SyntaxHighlighter final : public Syntax::Highlighter {
+public:
+    SyntaxHighlighter() { }
+    virtual ~SyntaxHighlighter() override;
+
+    virtual bool is_identifier(u64) const override;
+
+    virtual Syntax::Language language() const override { return Syntax::Language::SQL; }
+    virtual void rehighlight(Palette const&) override;
+
+protected:
+    virtual Vector<MatchingTokenPair> matching_token_pairs_impl() const override;
+    virtual bool token_types_equal(u64, u64) const override;
+};
+
+}