This branch exists to allow folks (cmpilato, primarily) to play with
implementations of a new Master Passphrase feature -- a single
passphrase which is used in concert with an encryption mechanism to
protect disk-cached Subversion credentials.

See http://wiki.apache.org/subversion/MasterPassphrase and
http://subversion.tigris.org/issues/show_bug.cgi?id=4145 for details.