Add a c test for the diff problem described in issue #3362. The current result
is that the in-memory and file diff produce different results for this dataset.

* subversion/tests/libsvn_diff/diff-diff3-test.c
  (two_way_diff): Extend error message.
  (test_issue_3362): New function.
  (test_funcs): Add test_issue_3362 as XFail.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1436724 13f79535-47bb-0310-9956-ffa450edef68