Ev2 shims: Find the correct base_revision if none is given during when dumping a repo.
Ev2 shims: Find the correct base_revision if none is given during when dumping
a repo.

* subversion/libsvn_repos/dump.c
  (fetch_props_func, fetch_kind_func, fetch_base_func): If not given a base
    revision, assume the one previous to the current rev (rather than HEAD).

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