Add a test for why r1712927 was wrong.
Add a test for why r1712927 was wrong.

* subversion/tests/libsvn_fs_fs/fs-fs-pack-test.c
  (compare_0_length_rep): New test case.
  (test_funcs): Register new test.

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1717867 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion