Rename shift_bb() to shift()

Rename shift_bb() to shift(), and DELTA_S to SOUTH, etc.
to improve code readability, especially in evaluate.cpp
when they are used together:

    old b = shift_bb<DELTA_S>(pos.pieces(PAWN))
    new b = shift<SOUTH>(pos.pieces(PAWN))

While there fix some small code style issues.

No functional change.

src/psqt.cpp

@@ -23,8 +23,9 @@
 #include "types.h"
 
 Value PieceValue[PHASE_NB][PIECE_NB] = {
-{ VALUE_ZERO, PawnValueMg, KnightValueMg, BishopValueMg, RookValueMg, QueenValueMg },
-{ VALUE_ZERO, PawnValueEg, KnightValueEg, BishopValueEg, RookValueEg, QueenValueEg } };
+  { VALUE_ZERO, PawnValueMg, KnightValueMg, BishopValueMg, RookValueMg, QueenValueMg },
+  { VALUE_ZERO, PawnValueEg, KnightValueEg, BishopValueEg, RookValueEg, QueenValueEg }
+};
 
 namespace PSQT {