{decoder,player}/Control: add ReplayGain{Config,Mode} attributes

Don't use the global variables in class DecoderBridge; instead,
forward these values to the decoder thread via PlayerControl and
DecoderControl.

src/player/Control.hxx

@@ -26,6 +26,8 @@
 #include "thread/Thread.hxx"
 #include "CrossFade.hxx"
 #include "Chrono.hxx"
+#include "ReplayGainConfig.hxx"
+#include "ReplayGainMode.hxx"
 
 #include <exception>
 
@@ -167,6 +169,9 @@ struct PlayerControl {
 
 	CrossFadeSettings cross_fade;
 
+	ReplayGainConfig replay_gain_config;
+	ReplayGainMode replay_gain_mode = ReplayGainMode::OFF;
+
 	double total_play_time;
 
 	/**
@@ -463,6 +468,13 @@ public:
 		return cross_fade.mixramp_delay;
 	}
 
+	void LockSetReplayGain(const ReplayGainConfig &_config,
+			       ReplayGainMode _mode) {
+		const ScopeLock protect(mutex);
+		replay_gain_config = _config;
+		replay_gain_mode = _mode;
+	}
+
 	double GetTotalPlayTime() const {
 		return total_play_time;
 	}

src/player/Thread.cxx

@@ -342,6 +342,13 @@ Player::StartDecoder(MusicPipe &_pipe)
 	assert(queued || pc.command == PlayerCommand::SEEK);
 	assert(pc.next_song != nullptr);
 
+	{
+		/* copy ReplayGain parameters to the decoder */
+		const ScopeLock protect(pc.mutex);
+		dc.replay_gain_config = pc.replay_gain_config;
+		dc.replay_gain_mode = pc.replay_gain_mode;
+	}
+
 	SongTime start_time = pc.next_song->GetStartTime() + pc.seek_time;
 
 	dc.Start(new DetachedSong(*pc.next_song),