Try to prune also when approximateEval < beta

Now we always try to filter out moves, we will have
more wasted evaluation calls, but also more pruned
nodes.

After 786 games

Mod vs Orig +196 =413 -177 +8 ELO

Verified also against Rybka it increases score to 50-51%

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

src/search.cpp

@@ -1517,8 +1517,6 @@ namespace {
               continue;
 
           // Value based pruning
-          if (approximateEval < beta)
-          {
           if (futilityValue == VALUE_NONE)
               futilityValue = evaluate(pos, ei, threadID) + FutilityValueMargin;
 
@@ -1531,7 +1529,6 @@ namespace {
               continue;
           }
       }
-      }
 
       // Make and search the move
       pos.do_move(move, st, ci, moveIsCheck);