Merge branch 'master' into clusterMergeMaster12

fixes minor merge conflicts

looks good:

Score of cluster vs master: 15 - 1 - 134  [0.547] 150
Elo difference: 32.5 +/- 17.5, LOS: 100.0 %, DrawRatio: 89.3 %

for 4 threads against 4x4 threads at 10+0.1s

src/cluster.h

@@ -26,6 +26,7 @@
 
 #include "tt.h"
 
+namespace Stockfish {
 class Thread;
 
 /// The Cluster namespace contains functionality required to run on distributed
@@ -119,6 +120,7 @@ inline void signals_sync() { }
 
 #endif /* USE_MPI */
 
+}
 }
 
 #endif // #ifndef CLUSTER_H_INCLUDED