Fixes typo in OS X bundle build script.
Changes SDL2 version in build-osx-libs.sh to Hg snapshot SDL-2.0.4-9134, refs #2852

git-svn-id: http://svn.wildfiregames.com/public/ps/trunk@15849 3db68df2-c116-0410-a063-a993310a9797
Merge 'remotes/trunk'