Teach svn_client_merge_peg5() to do an automatic merge when no revision
ranges are specified, and let 'svn merge' rely on that instead of calling
the dedicated automatic merge APIs.

This leaves the dedicated 'automatic merge' APIs in place for now; we might
want to remove them or make them private.

This reduces the amount of progress feedback displayed when running an
automatic merge with the new '--verbose' option: the two phases that were
introduced by 'Calculating automatic merge' and 'Merging' messages are now
introduced by a single 'Merging' message.

* subversion/include/svn_client.h,
  subversion/libsvn_client/merge.c
  (svn_client_merge_peg5): Do an automatic merge if no revision range is
    specified.
  (svn_client_merge_peg4): Tweak the doc string to account for this change.

* subversion/svn/merge-cmd.c
  (automatic_merge): Delete.
  (run_merge): Don't take special action to handle an automatic merge, let
    the pegged merge code path handle it.

* subversion/tests/cmdline/svntest/deeptrees.py
  (deep_trees_run_tests_scheme_for_merge): To keep the tests working, specify
    a revision range to the merge so that it will still be allowed even when
    using 'ignore ancestry'.  In other words, avoid invoking the automatic
    merge checks.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1463250 13f79535-47bb-0310-9956-ffa450edef68