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/timeman.cpp

@@ -29,11 +29,10 @@ namespace Stockfish {
 TimeManagement Time;  // Our global time management object
 
 
-// TimeManagement::init() is called at the beginning of the search and calculates
+// Called at the beginning of the search and calculates
 // the bounds of time allowed for the current game ply. We currently support:
 //      1) x basetime (+ z increment)
 //      2) x moves in y seconds (+ z increment)
-
 void TimeManagement::init(Search::LimitsType& limits, Color us, int ply) {
 
     // If we have no time, no need to initialize TM, except for the start time,