Derivation of sign value relies on shift right operator >> being an
arithmetic shift. It is thus not strictly portable since the C standard
defines the result of x >> y as "implementation-defined" when x is a
signed integer with a negative value.
Trellis quantization is modified:
- to work on the configurable spectral range Ss to Se
- to optionally optimize runs of EOBs
- to optionally split optimization between 2 spectral ranges
In trellis quantization passes Huffman table code optimization is
modified such as to generable a valid code length for each possible
symbol by resetting frequency counters to 1 instead of 0
