Add Stockfish namespace.

fixes #3350 and is a small cleanup that might make it easier to use SF
in separate projects, like a NNUE trainer or similar.

closes https://github.com/official-stockfish/Stockfish/pull/3370

No functional change.

src/timeman.cpp

@@ -24,6 +24,8 @@
 #include "timeman.h"
 #include "uci.h"
 
+namespace Stockfish {
+
 TimeManagement Time; // Our global time management object
 
 
@@ -95,3 +97,5 @@ void TimeManagement::init(Search::LimitsType& limits, Color us, int ply) {
   if (Options["Ponder"])
       optimumTime += optimumTime / 4;
 }
+
+} // namespace Stockfish