Did you get the new MediaWiki files via Git or by downloading the tarball?
If you got it via Git, you will need to install and update all of the dependencies yourself. See here for more information.
If you used the tarball, it appears that some of the files didn't get extracted properly or were possibly missed. Re-download the tarball and re-extract it to a new, empty folder. Then copy over your LocalSettings, updated versions of extensions, and images to the new folder. It's always recommended when upgrading with a tarball release to extract to a new folder as there may be issues caused by leaving around files from an old release that were removed in a future release.
Unless you are already familiar with using Git and feel comfortable with your systems administration skills, I recommend using the tarballs.