Removing all trailing whitespaces in src with a script included

Git often complains about trailing whitespaces in text files, e.g. it doesn't merge patches introducing new ones. To solve this problem and to enforce the conding conventions by replacing all tabs by four spaces (http://supertuxkart.sourceforge.net/Coding_Style#Layout), I've written a small python saved in tools/whitespace.py (tell me if you've got a better name) that can also do some statistics and ran it. That's the reason why the second commit is really huge, although it doesn't change the binary (Well, at least it with a good compiler. I still have to prove this.).