Add an early warning on scheduling a delete of the repository root in working
copies. (Some wc-db queries assume that the repository root is not moved,
so this makes it less likely for these invalid cases don't enter the database)

* subversion/libsvn_wc/delete.c
  (svn_wc__delete_many,
   svn_wc__delete_internal): Don't allow deleting paths that are switched to
     the repository root.

* subversion/tests/cmdline/input_validation_tests.py
  (delete_repos_root): Remove XFail marker and allow some output before the error.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1448366 13f79535-47bb-0310-9956-ffa450edef68