Retire CenterBind

And compensate in the PSQT.

STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 27714 W: 5161 L: 5052 D: 17501

LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 36354 W: 5008 L: 4909 D: 26437

Bench: 8603285

Resolves #556

src/pawns.cpp

@@ -59,9 +59,6 @@ namespace {
     S( 0,  0), S( 0,  0), S(0, 0), S(0, 0),
     S(20, 20), S(40, 40), S(0, 0), S(0, 0) };
 
-  // Center bind bonus, when two pawns controls the same central square
-  const Score CenterBind = S(16, 0);
-
   // Weakness of our pawn shelter in front of the king by [distance from edge][rank]
   const Value ShelterWeakness[][RANK_NB] = {
     { V( 97), V(21), V(26), V(51), V(87), V( 89), V( 99) },
@@ -103,10 +100,6 @@ namespace {
     const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
     const Square Left  = (Us == WHITE ? DELTA_NW : DELTA_SE);
 
-    const Bitboard CenterBindMask =
-      Us == WHITE ? (FileDBB | FileEBB) & (Rank5BB | Rank6BB | Rank7BB)
-                  : (FileDBB | FileEBB) & (Rank4BB | Rank3BB | Rank2BB);
-
     Bitboard b, neighbours, doubled, supported, phalanx;
     Square s;
     bool passed, isolated, opposed, backward, lever, connected;
@@ -198,9 +191,6 @@ namespace {
     b = e->semiopenFiles[Us] ^ 0xFF;
     e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
 
-    b = shift_bb<Right>(ourPawns) & shift_bb<Left>(ourPawns) & CenterBindMask;
-    score += CenterBind * popcount<Max15>(b);
-
     return score;
   }
 

src/psqt.cpp

@@ -34,9 +34,9 @@ const Score Bonus[][RANK_NB][int(FILE_NB) / 2] = {
    { S(  0, 0), S(  0, 0), S(  0, 0), S( 0, 0) },
    { S(-19, 5), S(  1,-4), S(  7, 8), S( 3,-2) },
    { S(-26,-6), S( -7,-5), S( 19, 5), S(24, 4) },
-   { S(-25, 1), S(-14, 3), S( 16,-8), S(31,-3) },
-   { S(-14, 6), S(  0, 9), S( -1, 7), S(17,-6) },
-   { S(-14, 6), S(-13,-5), S(-10, 2), S(-6, 4) },
+   { S(-25, 1), S(-14, 3), S( 20,-8), S(35,-3) },
+   { S(-14, 6), S(  0, 9), S(  3, 7), S(21,-6) },
+   { S(-14, 6), S(-13,-5), S( -6, 2), S(-2, 4) },
    { S(-12, 1), S( 15,-9), S( -8, 1), S(-4,18) },
    { S(  0, 0), S(  0, 0), S(  0, 0), S( 0, 0) }
   },