Add rudimentary MOVe support to BDB by simply recording add-with-history
instead of true moves.  In combination with the auto-move feature (see
later commits), this will still result in most of these adds being treated
as if they were proper moves.

* subversion/libsvn_fs_base/tree.c
  (base_revision_link): implement future API function

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1525432 13f79535-47bb-0310-9956-ffa450edef68