Revert "Remove skipQuiets variable in search()"

This reverts commit 76d2f5b.

Due to a bug, see #2019

Bench: 3516616

src/search.cpp

@@ -569,7 +569,7 @@ namespace {
     Depth extension, newDepth;
     Value bestValue, value, ttValue, eval, maxValue, pureStaticEval;
     bool ttHit, ttPv, inCheck, givesCheck, improving;
-    bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture;
+    bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture;
     Piece movedPiece;
     int moveCount, captureCount, quietCount;
 
@@ -879,12 +879,12 @@ namespace {
                                       ss->killers);
     value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
 
-    moveCountPruning = false;
+    skipQuiets = false;
     ttCapture = ttMove && pos.capture_or_promotion(ttMove);
 
     // Step 12. Loop through all pseudo-legal moves until no moves remain
     // or a beta cutoff occurs.
-    while ((move = mp.next_move(moveCountPruning)) != MOVE_NONE)
+    while ((move = mp.next_move(skipQuiets)) != MOVE_NONE)
     {
       assert(is_ok(move));
 
@@ -913,9 +913,8 @@ namespace {
       movedPiece = pos.moved_piece(move);
       givesCheck = gives_check(pos, move);
 
-      // Skip quiet moves if movecount exceeds our FutilityMoveCount threshold
-      moveCountPruning = depth < 16 * ONE_PLY
-                      && moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY];
+      moveCountPruning =   depth < 16 * ONE_PLY
+                        && moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY];
 
       // Step 13. Extensions (~70 Elo)
 
@@ -973,7 +972,10 @@ namespace {
           {
               // Move count based pruning (~30 Elo)
               if (moveCountPruning)
+              {
+                  skipQuiets = true;
                   continue;
+              }
 
               // Reduced depth of the next LMR search
               int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;