Revision 1497975

Switch the config name and semantics to busted-proxy.

For now, it retains the static configuration-based behavior. Future
work will perform runtime detection.

* subversion/include/svn_config.h:
  (SVN_CONFIG_OPTION_HTTP_CHUNKED_REQUESTS): renamed to ...
  (SVN_CONFIG_OPTION_BUSTED_PROXY): ... this

* subversion/libsvn_ra_serf/ra_serf.h:
  (svn_ra_serf__session_t): change USING_PROXY to boolean. add
    BUSTED_PROXY flag (loaded from config)

* subversion/libsvn_ra_serf/serf.c:
  (load_config): load the BUSTED_PROXY configuration data. if a proxy
    is being used and the proxy may be busted, then disable chunked
    requests
  (svn_ra_serf__open): initialize USING_CHUNKED_REQUESTS

* subversion/libsvn_subr/config_file.c:
  (svn_config_ensure): rename flag and adjust description