packaging: Fixed Cmake file.

- Only link static boost under Apple.
- Check if boost was found or print an error.
- Include additional lib64 libraries dirs when calling find_library() to
  fix issues with OpenSuse.


git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@2529 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534