Added system-volume-warning patch from nodevel

Added the patch as asked. I have renamed the patch to better comply with the "official" naming scheme. However, this could cause problems for people who have already installed my patch from OpenRepos, as there will be two duplicate patches, accessing the same file.
On the other hand, leaving the same name might create problems with file ownership. If you would like me to revert to the old name, feel free to reject the pull request.