Allow NULL streams to be converted from Perl.
Allow NULL streams to be converted from Perl.

* swigutil_pl.c
  (svn_swig_pl_make_stream): Handle the case that stream is undef.

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