This is a patch to fix "Modification of a read-only value attempted at..."
errors which were preventing XML-based modules in WebFetch 0.10 from
working on Perl 5.004_xx.  (This is not needed for Perl 5.005_xx.)

This patch was written by Ian Kluft <ikluft@thunder.sbay.org>.

*** Expat.xs.orig	Sat Sep 25 03:54:45 1999
--- Expat.xs	Sat Sep 25 03:55:04 1999
***************
*** 34,40 ****
  #define DTB_GROW 4096
  
  #define XMLP_UPD(fld) \
!   RETVAL = cbv->fld ? newSVsv(cbv->fld) : &PL_sv_undef;\
    if (cbv->fld) {\
      if (cbv->fld != fld)\
        Perl_sv_setsv(cbv->fld, fld);\
--- 34,40 ----
  #define DTB_GROW 4096
  
  #define XMLP_UPD(fld) \
!   RETVAL = cbv->fld ? newSVsv(cbv->fld) : newSVsv(&PL_sv_undef);\
    if (cbv->fld) {\
      if (cbv->fld != fld)\
        Perl_sv_setsv(cbv->fld, fld);\