bugfix: disable aq only when both aq-strength and cu-tree is off

AQ can be on when cutree is on even if aq-strength is 0.Do not force aq to be
off whenever aq strength is 0.
rc: add slow first pass as option. set turbo first pass as default in 2 pass

--HG--
extra : amend_source : a12d98c0ff3c89a86a6254aaa18014000c7f8abd
quant: remove TODO comment

Yes, there is a reason to check maxAbsLevel < 3 here, diffLevel below can only
be 0, 1, or 2.
psy-rdoq: fix unquant shift factors

dequant coefficients are made with s_invQuantScales[rem] << 4, so to perform an
unquant we must remove those four bits from dequantCoeff