Add XFailing test for a property diff that has missing intermediate  context lines.
Add XFailing test for a property diff that has missing intermediate 
context lines.

Runnning:
  diff -u <(svn pg prop iota@BASE) <(svn pg prop iota)
gives the right result, e.g. all context lines that should be there are
there and the hunk header offsets are right.

* subversion/tests/cmdline/diff_tests.py
  (diff_prop_missing_context): New. 
  (tests_list): Add the new test.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@978856 13f79535-47bb-0310-9956-ffa450edef68

wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion