Update search.cpp

At PvNodes allow bonus for prior counter move that caused a fail low
for depth 1 and 2. Note : I did a speculative LTC on yellow STC patch
since history stats tend to be highly TC sensitive

STC (Yellow):
LLR: -2.96 (-2.94,2.94) [0.00,5.00]
Total: 64295 W: 13042 L: 12873 D: 38380
http://tests.stockfishchess.org/tests/view/5af507c80ebc5968e6524153

LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 22407 W: 3413 L: 3211 D: 15783
http://tests.stockfishchess.org/tests/view/5af85dd40ebc591fdf408b87

Also use local variable excludedMove in NMP (marotear)

Bench:  5294316

src/search.cpp

@@ -737,7 +737,7 @@ namespace {
         && (ss-1)->statScore < 22500
         &&  eval >= beta
         &&  ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
-        && !ss->excludedMove
+        && !excludedMove
         &&  pos.non_pawn_material(pos.side_to_move())
         && (ss->ply >= thisThread->nmp_ply || ss->ply % 2 != thisThread->nmp_odd))
     {
@@ -1153,7 +1153,7 @@ namespace {
             update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY));
     }
     // Bonus for prior countermove that caused the fail low
-    else if (    depth >= 3 * ONE_PLY
+    else if (   (depth >= 3 * ONE_PLY || PvNode)
              && !pos.captured_piece()
              && is_ok((ss-1)->currentMove))
         update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth));