Merge r1560690 from trunk:

 * r1560690
   Fix repository-WC copies into relocated working copies and some wc-wc
   copy problems.
   Justifiation:
     It should be impossible to break a working copy by just copying something
     into it.
   Notes:
     r1560701 is a regression test for this problem, but can't be backported
     without resolving a minor text conflict.
   Votes:
     +1: rhuijben, brane, stefan2


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.7.x@1561441 13f79535-47bb-0310-9956-ffa450edef68