Set HistoryMax infinitely high

Respin this old idea. Earlier we tried only
with < 1000 games and result was inconclusive.

After 5845 games
Mod vs Orig: 935 - 936 - 3974 ELO (+-3.6)

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/history.h

@@ -70,8 +70,9 @@ private:
 /// the effect that parts of the search tree which have been searched
 /// recently have a bigger importance for move ordering than the moves which
 /// have been searched a long time ago.
+/// Current policy is to set this as high as possible, but avoid overflow.
 
-const int HistoryMax = 50000 * ONE_PLY;
+const int HistoryMax = (1 << 28);
 
 
 ////