Unify the meaning of ARG in svn-status-get-specific-revision.
Unify the meaning of ARG in svn-status-get-specific-revision.

* contrib/client-side/psvn/psvn.el
  (svn-status-get-specific-revision): Changed the sense of the prefix
    argument to match the docstring, and clarified the docstring.

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