Fix coverity 113065 (CWE-484)

[mayeut]

@detonin,

I'm almost sure the fall through is intentional otherwise nothing would work but, just to be sure, can you confirm ?
The added comment will tell coverity not to report an issue & the code will be clearer for everyone.

[detonin]

@mayeut yes this is intentional and can be merged.
What I actually wonder is if we need to keep t1_generate_luts where it currently is. It has been used to generate a static file (t1_luts.h) but there is no need to compile it each time we compile OpenJPEG: I think we should keep t1_luts.h and move t1_generate_luts in the tools folder for instance.

[mayeut]

@detonin, agreed for the file location. I'll let you create an issue for this as a reminder.

[detonin]

@mayeut #831