Long Diagonal Tweaks

a) Reduce PSQT values along the long diagonals on non-central squares
and increase the LongDiagonal bonus accordingly. The effect is to penalise
bishops on the long diagonal which can not "see" the 2 central squares.
The "good" bishops still have more or less the same bonus as current master.

b) For a bishop on a central square, because of the "| s" term in the code,
the LongDiagonalBonus was always given. So while being there, remove the "| s"
and compensate the central Bishop PSQT accordingly.

Passed STC
LLR: 2.95 (-2.94,2.94) [0.00,4.00]
Total: 44498 W: 9658 L: 9323 D: 25517
http://tests.stockfishchess.org/tests/view/5b8992770ebc592cf2748942

Passed LTC
LLR: 2.95 (-2.94,2.94) [0.00,4.00]
Total: 63092 W: 10324 L: 9975 D: 42793
http://tests.stockfishchess.org/tests/view/5b89a17a0ebc592cf2748b59

Closes https://github.com/official-stockfish/Stockfish/pull/1760

bench: 4693901

src/evaluate.cpp

@@ -162,7 +162,7 @@ namespace {
   constexpr Score HinderPassedPawn   = S(  8,  0);
   constexpr Score KingProtector      = S(  6,  6);
   constexpr Score KnightOnQueen      = S( 21, 11);
-  constexpr Score LongDiagonalBishop = S( 22,  0);
+  constexpr Score LongDiagonalBishop = S( 46,  0);
   constexpr Score MinorBehindPawn    = S( 16,  0);
   constexpr Score Overload           = S( 13,  6);
   constexpr Score PawnlessFlank      = S( 19, 84);
@@ -351,7 +351,7 @@ namespace {
                                      * (1 + popcount(blocked & CenterFiles));
 
                 // Bonus for bishop on a long diagonal which can "see" both center squares
-                if (more_than_one(Center & (attacks_bb<BISHOP>(s, pos.pieces(PAWN)) | s)))
+                if (more_than_one(attacks_bb<BISHOP>(s, pos.pieces(PAWN)) & Center))
                     score += LongDiagonalBishop;
             }