With the simplification of new_revert_partial() in r1104185, the REVERT_ROOT parameter is not used. In fact, it is not used by this entire set of revert functions. So... nuke it. From orbit. It's the only way to be safe.
Also, fold revert_internal() into svn_wc_revert4().
* subversion/libsvn_wc/adm_ops.c: (revert_restore): remove REVERT_ROOT and adjust recursive call. (new_revert_internal): remove REVERT_ROOT and adjust call to revert_restore(). (new_revert_changelist): remove REVERT_ROOT and adjust recursive call. adjust call to new_revert_internal(). (new_revert_partial): remove REVERT_ROOT and adjust calls to new_revert_internal(). (revert_internal): removed. folded into ... (svn_wc_revert4): ... here. directly call new_revert_changelist() if we have any changelist_filters. call new_revert_internal() or new_revert_partial() depending upon the DEPTH parameter. add an error return for bogus DEPTH values.