(just acting along the normal). This solves some of the odd
behaviour with the previous implementation if the kart is
off track. The new way is now the default, but the 'push
towards driveline' can be set in stk_config.xml.
git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@11923 178a84e3-b1eb-0310-8ba1-8eac791a3b58