Add option to apply trellis quantization to the DC coefficients ( see
#57 ). May need further refinement to make sure block order during
trellis optimization matches order during coding.
Optimizes quantization matrix by minimizing reconstruction error based
on quantized coefficients.
Feature is controlled by cinfo->trellis_q_opt; disabled by default.
A new pass type trellis_pass is added. It defines a pass where trellis
quantization is done in the quantize_trellis() function.
Trellis quantization can be enabled by setting use_moz_defaults to 2 or
by using the -trellis option in cjpeg
Note that trellis does currently not work with scan optimization. Scan
optimization is disabled when trellis is enabled.
