horizontally flipped infobox image (integrated change from github - https://github.com/flameo/studip-bugbash-2013/commit/4680d80871d5f39449cc797df02f44ca051106cb), fixes #3382

git-svn-id: svn://develop.studip.de/studip/trunk@26068 c5b85792-5220-0410-ad23-ed5b6b8ad999