xrefs_test.go: remove dead code and associated imports (#174)
xrefs_test.go: remove dead code and associated imports (#174)

`tickets` written but never read
bzz/kythe,bzz/kythe,bzz/kythe,bzz/kythe,kythe/kythe,bzz/kythe,bzz/kythe,kythe/kythe,bzz/kythe,kythe/kythe,bzz/kythe,bzz/kythe,kythe/kythe,kythe/kythe,kythe/kythe,kythe/kythe,kythe/kythe,bzz/kythe,kythe/kythe,bzz/kythe,kythe/kythe,kythe/kythe,bzz/kythe