ratecontrol: prevent one layer of non-zero I-slice qp clipping [CHANGES OUTPUT].

This seems to have been an error importing RC code from x264. It could be responsible
for error reports on I-slices (after POC 0) having much higher QP/low visual quality.
Needs review.
vbv: log frame-average QPs for VBV; even when AQ is disabled.
asm: HADDD optimization for XOP
asm-primitives: Enable missing XOP primitives in HIGH_BIT_DEPTH
TComTrQuant: comparing >=0 of unsigned variable is always true
TComTrQuant: nits
cip: add is*AvailableCIP()

simplify no CIP case.
cmake: allow icpc to use vectorization if it likes