Revision 1555133

Get rid of the ever increasing number of private apis in svn_sorts.h by adding
a new private/svn_sorts_private.h file with the private parts and updating the
needed #include-s.
*AND*
Improve error reporting during xml parsing in ra_serf a bit.

For 1.9 the number of private apis in this public header more than doubled,
doubling the original filesize, while our policy is to never add private
functions in public headers.

* build.conf
  (libsvn_subr): Add export.

* subversion/include/private/svn_sorts_private.h
  New file, copied from ../svn_sorts.h.

* subversion/include/svn_sorts.h
  Remove everything possible in our private namespace. Keeping some
  references.

* subversion/libsvn_client/diff_local.c
* subversion/libsvn_client/import.c
* subversion/libsvn_client/info.c
* subversion/libsvn_client/list.c
* subversion/libsvn_client/merge.c
* subversion/libsvn_client/mergeinfo.c
* subversion/libsvn_client/status.c
* subversion/libsvn_delta/compat.c
* subversion/libsvn_fs_fs/cached_data.c
* subversion/libsvn_fs_fs/index.c
* subversion/libsvn_fs_fs/low_level.c
* subversion/libsvn_fs_fs/pack.c
* subversion/libsvn_fs_fs/temp_serializer.c
* subversion/libsvn_fs_fs/transaction.c
* subversion/libsvn_fs_x/index.c
* subversion/libsvn_fs_x/low_level.c
* subversion/libsvn_fs_x/pack.c
* subversion/libsvn_fs_x/transaction.c
* subversion/libsvn_ra/compat.c
* subversion/libsvn_ra_serf/inherited_props.c
* subversion/libsvn_ra_serf/lock.c
* subversion/libsvn_repos/dump.c
* subversion/libsvn_repos/fs-wrap.c
* subversion/libsvn_subr/cmdline.c
* subversion/libsvn_subr/hash.c
* subversion/libsvn_subr/mergeinfo.c
* subversion/libsvn_subr/sorts.c
* subversion/libsvn_wc/adm_ops.c
* subversion/libsvn_wc/diff_editor.c
* subversion/libsvn_wc/status.c
* subversion/libsvn_wc/wc_db.c
* subversion/libsvn_wc/wc_db_update_move.c
* subversion/mod_dav_svn/repos.c
* subversion/svn/log-cmd.c
* subversion/svn/propget-cmd.c
* subversion/svnadmin/svnadmin.c
* subversion/svnlook/svnlook.c
* subversion/tests/libsvn_subr/priority-queue-test.c
* subversion/tests/libsvn_wc/op-depth-test.c
  Fix includes.

* subversion/libsvn_ra_serf/util.c
  (expat_response_handler): Combine XML errors with our custom parser errors
    instead of only reporting one or the other.