Remove redundant argument in think()

We don't need to pass side_to_move because we can get
it directly from the position object.

Note that in benchmark we always used to pass '0' and
it was a bug, but with no effect because was used only
in time[] and increment[], set always to 0 for both
colors.

Also additional small cleanup while there.

No functional change.

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

src/benchmark.cpp

@@ -159,7 +159,7 @@ void benchmark(const string& commandLine) {
           cerr << "\nPerft " << maxDepth << " result (nodes searched): " << perftCnt << endl << endl;
           totalNodes += perftCnt;
       } else {
-          if (!think(pos, false, false, 0, dummy, dummy, 0, maxDepth, maxNodes, secsPerPos, moves))
+          if (!think(pos, false, false, dummy, dummy, 0, maxDepth, maxNodes, secsPerPos, moves))
               break;
           totalNodes += nodes_searched();
       }