Pick best moves one per cycle instead of sorting

Pick best moves one per cycle instead of sorting

When the move list is very small, like captures normally
are, it is faster to pick the best move with a linear
scan, one per cycle.

This has the added advantage that the picked capture move is
very possibly a cut-off move, so that other searches are
avoided. For non-captures it is still faster to sort in
advance.

Because scan-and-pick alghortim is not stable, node count
has changed.

After 885 games at 1+0
Mod vs Orig +196 =510 -179 50.96%  451.0/885

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