When flagging a tree conflict involving a deleted entry during update/switch,
record the deleted target path and target revision for use by the conflict
resolver.

This is an alternative fix for the issue addressed by r1617909, which was
reverted in r1617930.

* subversion/libsvn_wc/update_editor.c
  (complete_conflict): Expect a non-null new_repos_relpath. Callers should
   always provide one, even if it matches repos_relpath.
  (delete_entry): Instead of passing a NULL new_repos_relpath, determine
   the deleted target path (which is different in case of update vs. switch)
   so complete_conflict() will record information on it. 


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1617932 13f79535-47bb-0310-9956-ffa450edef68