So, they did it themselves, case closed?
Well, not for me, unfortunately, because I remember watching a documentary back in the day, in which Carrie Fisher said that she'd planned to do the stunt herself until chickening out, and a stunt-woman was brought in at the last second to do it with Mark Hamill. Now, I haven't been able to substantiate that, so it's just as good as in the rumor pile, alright? Still, I'd swear that I remember that. Plus, even if she did say it in an interview once, I suppose it's not out of the question that she was just being dodgy about having actually done it, for whatever reason.
Honestly I had no idea one way or the other. I just presumed they were stunt doubles because the camera was behind them so you couldn't see their faces.
Generally in film if an actor does their own stunt they try and make sure you can actually see it's them. Conversely if it's done with a double they tend to try and shoot it in such a way that you can't see their face.
I'm not saying that's *always* the case, but you'd think Lucas would want to take full advantage of actually seeing the actors do the swing.
A quick google image search
later and it appears they really did do it...or attempt to do it at least
Maybe the swing Fisher chickened out on was the sail barge one in Jedi? I do remember seeing a photo of her with a double wearing the metal bikini. In fact...*scrolls down* there we go