Revision 1663005

Follow-up to r1661252: Also consider revisions committed directly to the branch
valid.

See this thread for the use-case:
URL: http://mail-archives.apache.org/mod_mbox/subversion-dev/201502.mbox/%3C87385qrwjj.fsf@wandisco.com%3E
Subject: 1.8.x backport conflicts bot is red

* tools/dist/backport.pl 
  (backport_usage): Update documentation.
  (validate_branch_contains_named_revisions): Include revisions committed
    directly to the branch in the set of 'present' revisions.

* tools/dist/backport_branch_with_original_revision.dump:
    New file.

* tools/dist/backport_tests.py
  (backport_branch_with_original_revision): New test.