XCode fixes.

git-svn-id: http://box2d.googlecode.com/svn/trunk@252 cafe418c-1137-0410-84cc-357ec87a5d9b
GDC demo work.

git-svn-id: http://box2d.googlecode.com/svn/trunk@253 cafe418c-1137-0410-84cc-357ec87a5d9b