* Less Lengthy enum/macro names.
* Optimize computation of Spherical Harmonics.
* Reduce radiance cubemap size a bit. Higher resolution is not necessary.
* Remove STUDIOLIGHT_LIGHT_DIRECTION_CALCULATED (was not used).
* Do windowing on each component separately instead of using luminance.
* Use ITER_PIXELS to iterate on each pixels, using pixel center coords.
* Remove gpu_matcap_3components as it is only needed when creating the gputex.
* Fix a lot of confusion in axis denomination/swizzle.
These changes should not affect functionallity.
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