Some cleanup in the AST nodes.

src/shared/cplusplus/ASTfwd.h

@@ -83,6 +83,7 @@ class CoreDeclaratorAST;
 class CppCastExpressionAST;
 class CtorInitializerAST;
 class DeclarationAST;
+class DeclarationListAST;
 class DeclarationStatementAST;
 class DeclaratorAST;
 class DeclaratorIdAST;
@@ -143,6 +144,7 @@ class SimpleSpecifierAST;
 class SizeofExpressionAST;
 class SpecifierAST;
 class StatementAST;
+class StatementListAST;
 class StringLiteralAST;
 class SwitchStatementAST;
 class TemplateArgumentListAST;