Convert init of eval to async option

So to be done only once at startup and in the (unlikely)
cases that a relevant UCI parameter is changed, instead
of doing it at the beginning of each search.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/search.cpp

@@ -251,6 +251,7 @@ void Search::think() {
 
   Position& pos = RootPosition;
   Chess960 = pos.is_chess960();
+  EvalRootColor = pos.side_to_move();
   SearchTime.restart();
   TimeMgr.init(Limits, pos.startpos_ply_counter());
   TT.new_search();
@@ -276,9 +277,6 @@ void Search::think() {
       }
   }
 
-  // Read UCI options: GUI could change UCI parameters during the game
-  read_evaluation_uci_options(pos.side_to_move());
-
   UCIMultiPV = Options["MultiPV"];
   SkillLevel = Options["Skill Level"];