Compute pinned and friends incrementally

In do_move() use previous pinned bitboards values to compute
the new one after the move. In particulary we end up with the
same bitboards in most cases. So detect these cases and just
keep the old values.

This should speedup a lot this slow computation in a very hot
path so that we can use this important info everywhere in the
code at very cheap cost.

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