Added setting for smoothing normals (default is still off till all tracks are fixed).

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@7601 178a84e3-b1eb-0310-8ba1-8eac791a3b58

data/stk_config.xml

@@ -36,6 +36,9 @@
        Penalty: Penalty time if a kart accelerates before GO. -->
   <startup penalty="1" />
 
+  <!-- If the normals (for wheel raycasts) should be smoothened -->
+  <physics smooth-normals="true"/>
+
   <!-- The title music. -->
   <music title="main_theme.music"/>