Constify some parameters.
Constify some parameters.

* subversion/libsvn_wc/upgrade.c:
  (upgrade_to_wcng, upgrade_working_copy): constify the DATA param
  (struct upgrade_working_copy_baton_t): constify the DATA member

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