[Retros] Add units: 17th update (1RA)

[Mu-Tsun Tsai]

Andy's pawn formation suggested an improvement on an older 1RA design that I 
have in mind (unpublished).

Diagram:
http://www.janko.at/Retros/d.php?ff=8/PP6/1PR5/1BQ5/P7/PkN5/NP1P4/2K5
(13+1)

Stip: Add the missing unit(s).

Intended solution: +wRd1 (last move: O-O-O)



Mu-Tsun