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/search.cpp

@@ -1588,8 +1588,8 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
 /// fail high at root. We try hard to have a ponder move to return to the GUI,
 /// otherwise in case of 'ponder on' we have nothing to think on.
 
-bool RootMove::extract_ponder_from_tt(Position& pos)
-{
+bool RootMove::extract_ponder_from_tt(Position& pos) {
+
     StateInfo st;
     bool ttHit;