Additional fix for issue 4339, diff suffix scanning invalid read
at last chunk boundary.

* subversion/libsvn_diff/diff_file.c
  (find_identical_suffix): Handle file ending at end of chunk in all cases.

* subversion/tests/libsvn_diff/diff-diff3-test.c
  (test_token_compare): Extend.

Patch by: jcorvel, me


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1462041 13f79535-47bb-0310-9956-ffa450edef68