[Note from the future: reverted in r1241635.]
[Note from the future: reverted in r1241635.]

Ev2 shims: Don't attempt to drive an editor multiple times.

Current number of Ev2 test failures: 9

* subversion/libsvn_delta/compat.c
  (editor_baton): New driven member.
  (complete_cb): Mark the editor driven.
  (abort_db): Don't drive the editor a second time if it's already been tried.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion