LMP tweak - #54

LMP tweak

STC:
ELO   | 6.22 +- 4.62 (95%)
SPRT  | 10.0+0.10s Threads=1 Hash=16MB
LLR   | 2.95 (-2.94, 2.94) [0.00, 5.00]
GAMES | N: 11056 W: 2920 L: 2722 D: 5414

LTC:
ELO   | 6.62 +- 4.70 (95%)
SPRT  | 60.0+0.60s Threads=1 Hash=256MB
LLR   | 3.01 (-2.94, 2.94) [0.00, 5.00]
GAMES | N: 9872 W: 2425 L: 2237 D: 5210

Bench: 2141682

src/search/search_thread.h

@@ -356,7 +356,7 @@ namespace search {
                         }
                     }
 
-                    if (depth <= 5 && made_moves >= 5 + depth * depth / (2 - improving)) {
+                    if (depth <= 6 && made_moves >= (5 + depth * depth) / (2 - improving)) {
                         skip_quiets = true;
                     }