Log Message:
Update to 0.55.

Upstream changes:

[Changes for 0.55 - Feb 1, 2005]

* Partially support remote copies that cross local mirror anchors
  with cb_copy_notify callback.

* Fix a pool issue that session of ra->get_commit_editor is not
  recycle due to ref holding in the wrong pool.

* Cope with latest svn-trunk ra api changes.