Lighting fixes? Plane and simple!

Continuing my recent streak of making random lighting/colormap-related fixes to long-standing bugs:

• Fix that thing where ALL transparent FOF planes were continuously fullbright unless encased in a fog which disables sprite fullbrightness, which was long-hated by many people in the community!

  • For backwards compatibility, setting flag 1 in that fog field (which is probably the most common "in-the-wild" usage of this feature) will continue to make objects un-fullbright.
  • For situations where you desperately want the fullbright plane behaviour to be enabled, you can apply fog flag 2.

• Change the fadestart and fadeend range in which colormaps are generated.

  • The problem HERE was that the darkest light level reached by generated colormaps was actually slightly brighter than the darkest level reached by normal colormaps.
  • The typo I fixed does have SOME basis in fact - standard colormap lumps are 34 (33 in 0-indexing) long rather than 32 (31), but whoever wrote this didn't realise that the code for generating them didn't do it DooM style, just bright-to-dark with no extras on the end...
  • Thanks to Sryder for his help tracking this one down.

Because this adds some fidelity to the feature that was not there before, you may wish for this to go to next. However, I consider the original behaviour a bug, and it's rendering only, so it might as well go into master.

You are welcome to contact me in direct messages for a test file!