r950445 changed the semantics of svn_io_dir_walk() to also pass APR_LNK filetypes to the provided callback function. After some list discussion, I think this violates our compatability promises. So I'm effectively reverting svn_io_dir_walk() to its original behavior, and revving the API to include the new behavior.
### NOTE: Had to fix the recursion in svn_io_dir_walk2() in r967198. ###
* subversion/libsvn_subr/io.c (svn_io_dir_walk2): Renamed from svn_io_dir_walk().
* subversion/libsvn_subr/deprecated.c (walk_func_filter_baton_t, walk_func_filter_func): New callback function and baton. (svn_io_dir_walk): Recreate here as just a wrapper around svn_io_dir_walk2() which uses a filtering callback function to ensure the promised semantics.
* subversion/libsvn_repos/repos.c (svn_repos_hotcopy): Use svn_io_dir_walk2() instead of svn_io_dir_walk().