Update tibblify() (and related components) to be an S7 generic, dispatching on both x and spec. For now spec will always be NULL (invoking guessing) or an S3 tspec (or other things that we deal with the same way tibblify() already does). The S3 tspecs will invoke the "old" tibblify for the most part. We'll also update finalize_tspec_object() to an S7 generic as part of this, and anything else that's directly related to tibblify(). We won't implement the S7 tspec class here, nor things related to that (like updating guess_tspec()).
Update
tibblify()(and related components) to be an S7 generic, dispatching on bothxandspec. For nowspecwill always beNULL(invoking guessing) or an S3 tspec (or other things that we deal with the same waytibblify()already does). The S3 tspecs will invoke the "old" tibblify for the most part. We'll also updatefinalize_tspec_object()to an S7 generic as part of this, and anything else that's directly related totibblify(). We won't implement the S7 tspec class here, nor things related to that (like updatingguess_tspec()).