Investigate MQC_PERF_OPT

[rouault]

The MQC decoder has a MQC_PERF_OPT mode that is disabled currently. It was introduced originally per 627f484

Evaluate if it is functionally equivalent and performance impacts

[rouault]

@detonin @CharlesBuysschaertIntopix

The ASAN target of Travis tests showed that there was a memory issue that is now fixed per
rouault@755cc0f and now the tests are all good : https://travis-ci.org/rouault/openjpeg/builds/231321333

However I can't see performance improvements. With the basic list of tests, the timings are essentially the same with or without the optimization. But with the "testovani" suite, the total execution time in MQC_PERF_OPT mode is ~ 190 s, whereas with master it is ~ 167 s, so a clear performance regression. Probably because the optimization requires to do an extra pass on the codestream.

[rouault]

Closing with removal of MQC_PERF_OPT