[Retros] last move type D / PxN=N/PxN=N case

[raosorio at fibertel.com.ar]

Hi Mario,

Andrew made a clever  improvement on the PxN=N/PxN=N case.
We have agreed to join the authorship,

Roberto Osorio, Jorge Lois & Andrew Buchanan
PxN=N/PxN=N/22            1Nqkrb2/1pppp1p1/p7/8/8/7P/1P1PPPP1/2BRKQn1 22/224

On the other hand, Andrew also detected a sutil detail in the K-/PxQ=Q case that has 
to be changed.

Jorge Lois, Roberto Osorio & Andrew Buchanan
K-/PxQ=Q/21             8/1ppp1Pp1/1p2p3/8/8/2P2PP1/1PPkPK1P/NRRq3q

Best,
Roberto