Generate quiet checks in QS at early depths

[jhonnold]

Bench: 5806344

ELO | 5.39 +- 3.51 (95%) SPRT | 8.0+0.08s Threads=1 Hash=8MB LLR | 2.96 (-2.94, 2.94) [0.00, 3.00] GAMES | N: 18368 W: 4631 L: 4346 D: 9391 http://chess.grantnet.us/test/33217/

ELO | 7.36 +- 4.18 (95%) SPRT | 40.0+0.40s Threads=1 Hash=64MB LLR | 2.97 (-2.94, 2.94) [0.00, 3.00] GAMES | N: 12424 W: 3053 L: 2790 D: 6581 http://chess.grantnet.us/test/33218/