Change license to MIT/PSF to match xattr project (so we can contribute it).
Change license to MIT/PSF to match xattr project (so we can contribute it).

git-svn-id: 81e381228600e5752b80483efd2b45b26c451ea2@1484 e27351fd-9f3e-4f54-a53b-843176b1656c

trevor/calendarserver,trevor/calendarserver,trevor/calendarserver