Fix -xbuttons window width GTK

Because Label options not followed by a SAME_ROW element were only
packed into the first two columns of the dialog table, the board window
reserved space for a third column behind the message window if there
was no button bar.
Attempt to make GTK sizing work with tiling WM

The Rezise routine now takes the size of the entire dialog table
(for me always equal to the outer-window size), and checks if the
actual outer window is smaller. If it is, it shrinks the board to fit,
under the assumption that a tiling window manager offers only a limited
'viewport' to our dialog, and we want everything to be visible inside that.
Fix promotion in Betza move generator

The Betza move generator was geenrating allmoves as NormalMove, but in
that case XBoard would not allow the move to have a promotion suffix.
Now Pawns and Lances reaching last rank will be assumed to promote.
Also do dual-royal test in variant shogi

For the benefit of Sho Shogi we also have to be prepared to find a
Crown Prince in variant shogi, so it can be used as a parent variant
for Sho Shogi with legality testing on.
Add persistent Boolean option -fixedSize

When set, this option suppresses sizing of the board and clocks when
the window is sized by the user. This is achieved by wrapping the entire
dialog in a non-expanding hbox.
removed gtk theme from OSX app