Fix build break due to missing XML_StopParser from old Expat libs.
Fix build break due to missing XML_StopParser from old Expat libs.

* subversion/libsvn_ra_serf/util.c:
  (EXPAT_HAS_STOPPARSER): new symbol if Expat has XML_StopParser
  (expat_start, expat_end, expat_cdata): use EXPAT_HAS_STOPPARSER

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