Add Generic tuple instances up to 15-tuple
Add Generic tuple instances up to 15-tuple

Why 15? Because we have Eq instances up to 15.

Metric Increase:
    T9630
    haddock.base

sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc