Fix quantization factor allocation

We don't need to wastefully allocate quant tables above QP_MAX_SPEC; they're
never used.
v210 input support

Assembly based on code by Henrik Gramner and Loren Merritt.
Add support for AVC-Intra Class 200
x86inc: speed up compilation with yasm

Work around yasm's inefficiency with handling large numbers of variables
in the global scope.