Finish implementation of Shogi

Finish implementation of Shogi

Shogi promotions were implemented by introducing a new promoType
value (3), which can be set y 'S' in the board status line.
Demotion of pieces takes place on capture, by tracing them back with
was_promoted() to their original, which now is not automatically Pawn,
but derived from the piece mentioned in the move string.

Like in Bughouse a promoted Queen is not distinguished from a
primordial one on the board, Golds which are promoted Pawns / Lances /
Knights / Silvers all look the same as a primordial Gold. The Dragon
Horse and Draon King look different from Bishop and Rook, though, and
are indicated by the letters I and J on the board.

The promotion is indicated in the SAN move by suffix =G, =I or =J.
Deferral is not indicated. On input == is understood as deferral, =+ or
=^ (or in fact =<ANY PIECE> as promotion).