Clean up comments in code

- Capitalize comments
- Reformat multi-lines comments to equalize the widths of the lines
- Try to keep the width of comments around 85 characters
- Remove periods at the end of single-line comments

closes https://github.com/official-stockfish/Stockfish/pull/5469

No functional change

src/search.h

@@ -236,8 +236,8 @@ class Worker {
    public:
     Worker(SharedState&, std::unique_ptr<ISearchManager>, size_t, NumaReplicatedAccessToken);
 
-    // Called at instantiation to initialize Reductions tables
-    // Reset histories, usually before a new game
+    // Called at instantiation to initialize reductions tables.
+    // Reset histories, usually before a new game.
     void clear();
 
     // Called when the program receives the UCI 'go' command.
@@ -256,7 +256,7 @@ class Worker {
    private:
     void iterative_deepening();
 
-    // Main search function for both PV and non-PV nodes
+    // This is the main search function, for both PV and non-PV nodes
     template<NodeType nodeType>
     Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
 
@@ -266,8 +266,7 @@ class Worker {
 
     Depth reduction(bool i, Depth d, int mn, int delta) const;
 
-    // Get a pointer to the search manager, only allowed to be called by the
-    // main thread.
+    // Pointer to the search manager, only allowed to be called by the main thread
     SearchManager* main_manager() const {
         assert(threadIdx == 0);
         return static_cast<SearchManager*>(manager.get());