Discount score when mating potential in jeopardy

Discount score when mating potential in jeopardy

A new routine is added to the search, to determine the right-shift of
the score when the leading side does nor have mating potential, its last
Pawn is in jeopardy and no mating potential will be left, or when it has
no Pawns to begin with (even with mating potential). The heuristic for
mating potential can be fine-tuned by hiding some flags in the pair bonus
field, for 'mating minor', 'deficient pair' or 'tough defender'.