This is actually unsupported (because LiClipse itself may break because of inner dependencies to PyDev, the PyDev version is fixed)...
Now, having said that, you can generate a new PyDev build locally following the instructions from
http://www.pydev.org/developers.html with the same version that is used in LiClipse -- which still hasn't been updated in git, so, you probably are good to go without any additional version renumbering -- and then install that version on your running LiClipse as you'd install any regular plugin (through help > install new software > point to the location in the filesystem where you created that build) -- note that I haven't actually tested it, but in theory it should work (and I don't think there has been any great breakage in the APIs from the latest release to the latest commit, so, it should be something reasonably safe at this point).