Recent GNU Chess changes

[Simon Waters]

The CVS version of GNU Chess on Savannah has had some additions
since the release of GNU Chess 5.03.

1. The build procedure for CygWin was fixed.

2. Errors handling illegal moves that pass xboard/winboards
initial tests have been fixed. This was en-passant captures when
the last move was not the appropriate pawn move, castling when
the king has already moved. GNU Chess recognised them as
illegal, now it tells Winboard or Xboard about the illegality of
the moves. These bugs are thought to have been in GNU Chess 5
since it's initial release.

3. Added additional commands to cmd.c to satisfy parsing
required to avoid spurious "Illegal move:" errors.

4. Implemented basic "hint" function, showing next move in
principal variation if the PV has been calculated.

5. Implemented basic "st" function for a seconds per move time
control. Not 100% happy with this change, but better than
ignoring it.

I have some other changes to merge, and write, which I intended
to include in release 5.04. Do people feel strongly that the
illegal move problem should be fixed by an earlier release?

  Simon