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+- Have positions remember where both kings are; this will save a lot
+ of calls to chess-pos-search
+
+- Make use of the new chess-incr-index*, which does no checks
+
+- Don't popup the display if it's already the currently selected
+ window
+
- Make the drawing/highlighting code just touch single squares, rather
than redrawing the whole board each time (fast though this is,
touching single squares is all that's necessary, and it would be