Small bonus for a blocked passed pawn

In case of a blocked passed pawn we don't give any
additional bonus, with this patch we grant a small
bonus if the blocking piece is our own.

Passed STC:
LLR: 2.95 (-2.94,2.94) [-1.50,4.50]
Total: 63965 W: 10950 L: 10692 D: 42323

and LTC:
LLR: 2.95 (-2.94,2.94) [0.00,6.00]
Total: 19237 W: 2740 L: 2562 D: 13935

bench: 7859671