[llvm] r288424 - [ADT, Support, TableGen] Fix some Clang-tidy modernize-use-default and Include What You Use warnings; other minor fixes (NFC).

[Malcolm Parsons via llvm-commits]

>  protected:
>    // Workaround Clang PR22793
> -  ~basic_parser() {}
> +  ~basic_parser() = default;
>  };

PR22793 is about clang 3.6 crashing on class templates with defaulted
protected destructors.

If the workaround is still needed then revert this.
Otherwise, remove the comment.