Silence a good bunch of Intel warnings

Silence a good bunch of Intel warnings

Note that some pawns and material info has been switched
to int from int8_t.

This is a waste of space but it is not clear if we have a
faster or slower code (or nothing changed), some test should be
needed.

Few warnings still are alive.

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