remove blank line between function and it's description

- remove the blank line between the declaration of the function and it's
  comment, leads to better IDE support when hovering over a function to see it's
  description
- remove the unnecessary duplication of the function name in the functions
  description
- slightly refactored code for lsb, msb in bitboard.h There are still a few
  things we can be improved later on, move the description of a function where
  it was declared (instead of implemented) and add descriptions to functions
  which are behind macros ifdefs

closes https://github.com/official-stockfish/Stockfish/pull/4840

No functional change

src/tt.h

@@ -37,7 +37,6 @@ namespace Stockfish {
 // move       16 bit
 // value      16 bit
 // eval value 16 bit
-
 struct TTEntry {
 
     Move  move() const { return Move(move16); }
@@ -65,7 +64,6 @@ struct TTEntry {
 // contains information on exactly one position. The size of a Cluster should
 // divide the size of a cache line for best performance, as the cacheline is
 // prefetched when possible.
-
 class TranspositionTable {
 
     static constexpr int ClusterSize = 3;