Related to issue #1520:  throw better mod_dav_svn error.
Related to issue #1520:  throw better mod_dav_svn error.

* mod_dav_svn/deadprops.c (save_value): use the error message text
  from the libsvn_repos error if possible, rather than a generic message.

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