Revision 1502401

Reimplement the tristate http-chunked-requests config option on top of the
latest trunk implementation of boolean http-detect-chunking.

* subversion/include/svn_config.h
  (SVN_CONFIG_OPTION_HTTP_DETECT_CHUNKING): Renamed to ...
  (SVN_CONFIG_OPTION_HTTP_CHUNKED_REQUESTS): New.

* subversion/libsvn_ra_serf/serf.c
  (load_config): Switch to using the tristate option.

* subversion/libsvn_ra_serf/util.c
  (svn_ra_serf__error_on_status): Suggest the tristate option be set to auto
    or no when we get a 411.

* subversion/libsvn_subr/config_file.c
  (svn_config_ensure): Update to reflect change in config option.

Suggested by: gstein
(Greg suggested this could be implemented much more simply than the prior
 version of this branch did.)