Data.Ord: add a field name and derived instances to Down

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Please take a few moments to verify that your commits fulfill the following:

• are either individually buildable or squashed
• have commit messages which describe what they do (referring to [Notes][notes] and tickets using #NNNN syntax when appropriate)
• have added source comments describing your change. For larger changes you likely should add a [Note][notes] and cross-reference it from the relevant places.
• add a testcase to the testsuite.
• [x]

Proposal: https://mail.haskell.org/pipermail/libraries/2019-May/029572.html