[MERGE] Test for bug #272444 (symlinks to Unicode file names)

[Daniel Clemente]

Could someone please check this patch in? Now it's semi-approved.
  http://bundlebuggy.aaronbentley.com/project/bzr/request/<87d4hmvnf1.fsf%40yahoo.com>

  That patch applies well against today's trunk.

  The tests fail since the bug is still there. There seems to be some UnicodeWarning too, but they come from the failing code, not from the test case, so it's not something the test can change.
   But the test can be checked in -before the bug is corrected- in order to help the fixture of bzrlib's code.

Daniel