{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/Partition.cxx

@@ -23,6 +23,7 @@
 #include "DetachedSong.hxx"
 #include "mixer/Volume.hxx"
 #include "IdleFlags.hxx"
+#include "ReplayGainGlobal.hxx"
 
 Partition::Partition(Instance &_instance,
 		     unsigned max_length,
@@ -50,6 +51,8 @@ Partition::UpdateEffectiveReplayGainMode(ReplayGainMode mode)
 		    ? ReplayGainMode::TRACK
 		    : ReplayGainMode::ALBUM;
 
+	pc.LockSetReplayGain(replay_gain_config, mode);
+
 	outputs.SetReplayGainMode(mode);
 }