Implement Last Seconds Noise (LSN) filtering

Implement Last Seconds Noise (LSN) filtering

When an engine is in deep trouble at few
seconds from time limit then giveup without
fighting anymore.

This is used to reduce "lucky draws" and time pressure
blunders noises that can obfuscate results during tests
blitz games (typical one minute games).

Goal of this technique is to reduce number of matches
needed to reliably prove then an engine A is stronger
then an opponent B.

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