API: deprecate rename_axis / reindex_axis ?
Given we are adding the "labels, axis=0/1" idiom to `reindex` and `rename` itself (https://github.com/pandas-dev/pandas/issues/12392, PR https://github.com/pandas-dev/pandas/pull/17800), I think the specific `reindex_axis` and `rename_axis` will be superfluous.

Should be deprecate them?