Deprecate the RA->open_tmp_file callback. It was from a long time ago, when we did have not temp file capabilities. Today, RA layers should just use the available function for generating unique files (from svn_io.h)
* subversion/libsvn_client/ra.c: (open_admin_tmp_file): removed (open_tmp_file): use svn_io_open_unique_file3 to always generate a temp file in the system temp area. (svn_client__open_ra_session_internal): always use open_tmp_file, ignoring the USE_ADMIN parameter.
* subversion/libsvn_ra_neon/commit.c: (commit_apply_txdelta): ... * subversion/libsvn_ra_neon/fetch.c: (make_reporter): ... * subversion/libsvn_ra_serf/commit.c: (apply_textdelta): ... use svn_io_open_unique_file3 rather than the open_tmp_file callback.