Fix a HunkParser typo, "identcal" -> "identical"
Summary: See rP3f8eccdaec8f85933bfea6ce5348bde25ced0489.
Test Plan: Read carefully.
Reviewers: amckinley, avivey
Reviewed By: avivey
Subscribers: avivey
Differential Revision: https://secure.phabricator.com/D20499