Quoting :doc note-6-5:

  The [brr@] command now supports inputs :initial-ttree and
  :final-ttree. Thanks to David Rager for a request leading to these
  enhancements. See [ttree] for a discussion of the tag-tree
  structures returned for these inputs.

  (GCL only) A restriction for structure-sharing (as described in a
  remark, ``Remark on print-circle-files''; see [print-control])
  involving GCL has been removed, since this is no longer required
  for the latest GCL versions (2.6.8 and 2.6.10). Thanks to Jared
  Davis and Camm Maguire for useful discussions and this GCL
  improvement.


git-svn-id: http://acl2-devel.googlecode.com/svn/trunk@1227 5d84a466-a78b-0930-a311-59b22171a541