I don’t believe that SVN has this feature built into the server product. I also don’t believe anything like this emulated in any clients that I have used, including TortoiseSVN.
To get around this problem, I have resorted to using a DVCS such as Git or Mercurial, to allow me to branch/merge/shelve locally before pushing the content back to SVN. It’s arguably a bit of a kludge, but it works really well.