Minor user-friendliness tweaks to the interactive conflict resolver.

* subversion/svn/conflict-callbacks.c
  (prompt_user): Say 'Unrecognized option' when we don't recognize the
    input.
  (handle_text_conflict): Tell the user why 'resolved' is not considered a
    valid input. Add some notes.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1447764 13f79535-47bb-0310-9956-ffa450edef68