Convert History table H in a local variable

This is a first step for future patches and in
any case seems a nice thing to do.

No functional change.

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

src/movepick.cpp

@@ -63,7 +63,8 @@ namespace {
 /// search captures, promotions and some checks) and about how important good
 /// move ordering is at the current node.
 
-MovePicker::MovePicker(const Position& p, bool pv, Move ttm, Depth d, SearchStack* ss) : pos(p) {
+MovePicker::MovePicker(const Position& p, bool pv, Move ttm, Depth d,
+                       const History& h, SearchStack* ss) : pos(p), H(h) {
 
   pvNode = pv;
   ttMove = ttm;