Faster handling of king captures in Position::see

Another SEE speed up that passed the SPRT short TC test!

LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 81337 W: 15060 L: 14745 D: 51532

No functional change.

src/position.cpp

@@ -1080,13 +1080,18 @@ int Position::see(Move m) const {
 
       // Locate and remove the next least valuable attacker
       captured = min_attacker<PAWN>(byTypeBB, to, stmAttackers, occupied, attackers);
-      stm = ~stm;
-      stmAttackers = attackers & pieces(stm);
 
       // Stop before processing a king capture
-      if (captured == KING && stmAttackers)
+      if (captured == KING)
+      {
+          if (stmAttackers == attackers)
+              ++slIndex;
+
           break;
+      }
 
+      stm = ~stm;
+      stmAttackers = attackers & pieces(stm);
       ++slIndex;
 
   } while (stmAttackers);