According to FSF, to use LGPL in my library, I have to include both the copy of GPL & LGPL. I understand that the reason being LGPL 3 is now written as additional permissions over GPL 3. However, as that's not the case for prior versions of LGPL, I understand that if I use LGPL 2.1 I only have to include a copy of LGPL 2.1. Is that correct?
And, as a side question, should I also include a copy of (L)GPL 3 too, given that it's now available, so that users can also know the additional rights (L)GPL 3 grants?