doxygen fixes.

src/GameplayAssist.h

@@ -13,7 +13,8 @@ public:
 	void Init();
 	/**
 	 * @brief Play the sounds in question for the particular chart.
-	 * @param nd the note data used for playing the ticks. */
+	 * @param nd the note data used for playing the ticks.
+	 * @param ps the player's state (and number) for Split Timing. */
 	void PlayTicks( const NoteData &nd, const PlayerState *ps );
 	/** @brief Stop playing the sounds. */
 	void StopPlaying();