Bug 935776: Revert "fixed SDL compilation in Lion, and enabled SDL compilation in Mac OS X"

This reverts commit 5957279f5b5a75787bba8011acbac044a1db9e62.
Merge pull request #66 from vicamo/bugzilla/935776/jb_revert-5957279

Bug 935776: Revert "fixed SDL compilation in Lion, and enabled SDL compilation in Mac OS X". r=mwu