Avoid double-closing of SVN::Stream objects.
Avoid double-closing of SVN::Stream objects.

* perl/Core.pm: undef svn_stream after close.

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