Clean out obsolete code and rename a type.
Clean out obsolete code and rename a type.

* subversion/libsvn_ra_serf/merge.c:
  (svn_ra_serf__merge_context_t): renamed to ...
  (merge_context_t): ... this, since it is now private
  (merge_closed, setup_merge_headers, create_merge_body,
      svn_ra_serf__run_merge): track the type rename
  (push_state, start_merge, end_merge, cdata_merge): removed.

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