Implement a fallback system when aspiration search fails low and we are out of time.

However also this patch is immediately reverted. For three reasons:
1) the case it affects is very rare (and then we are likely to lose anyway),
   so we can well live without this.

2) Because the case is so rare it's hard to test this change properly.

3) To perform fallback search, we must reset so many global variables that this
   patch is very likely both buggy and extremely bad style.

Consider including this again if we clean-up global variables one day...

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