Reviewed-by: Trust Me

Mainly comma tokens. Referencing all tokens is necessary to be able to
implement pretty-printing based on the AST while maintaining user
formatting.

Reviewed-by: Roberto Raggi

Added the ability to clone AST nodes. Please, note that this is not finished yet. So don't try to use it.

Accept the next-declarator in NewDeclaratorAST::accept() and implemented NewDeclarator::lastToken().