game: mention Oink

* doc/spot.bib (vandijk.18.tacas): New entry.
* spot/misc/game.hh (solve_parity_game): Mention it.

doc/spot.bib

@@ -856,6 +856,22 @@
   doi		= {10.1007/978-3-642-59126-6_7}
 }
 
+@InProceedings{	  vandijk.18.tacas,
+  author	= {Tom van Dijk},
+  title		= {Oink: An Implementation and Evaluation of Modern Parity
+		  Game Solvers},
+  booktitle	= {Proceedings of the 24th International Conference on Tools
+		  and Algorithms for the Construction and Analysis of Systems
+		  (TACAS'18)},
+  year		= 2018,
+  pages		= {291--308},
+  editor	= {Dirk Beyer and Marieke Huisman},
+  isbn		= {978-3-319-89960-2},
+  publisher	= {Springer},
+  series	= {Lecture Notes in Computer Science},
+  volume	= {10805}
+}
+
 @Article{	  zielonka.98.tcs,
   author	= {Wieslaw Zielonka},
   title		= {Infinite games on finitely coloured graphs with