dot: add support for two-player games

* spot/twaalgos/dot.cc: Honor the "state-player" property and draw
player 1 states using diamonds.
* doc/org/hoa.org: Show an example.
* tests/core/gamehoa.test: Make sure diamond is output.
* NEWS: Mention this.

doc/org/hoa.org

@@ -1220,3 +1220,17 @@ sed -n "s/^$h: \(.*\)\$/\\1/p" <<EOF  | tr -d '\n'
 $t
 EOF
 #+END_SRC
+
+When converted to dot, states from player 1 have a diamond shape:
+
+#+NAME: exgame.dot
+#+begin_src sh :exports code
+ltlsynt --ins=a --outs=b -f 'Ga <-> Gb' --print-game-hoa | autfilt --dot
+#+end_src
+
+#+BEGIN_SRC dot :file exgame.svg :var txt=exgame.dot :exports results
+$txt
+#+END_SRC
+
+#+RESULTS:
+[[file:exgame.svg]]