[Bf-codereview] Alpha premul pipeline cleanup (issue 7018048)

[brechtvanlommel at gmail.com]

https://codereview.appspot.com/7018048/diff/1/source/blender/render/intern/source/imagetexture.c
File source/blender/render/intern/source/imagetexture.c (right):

https://codereview.appspot.com/7018048/diff/1/source/blender/render/intern/source/imagetexture.c#newcode106
source/blender/render/intern/source/imagetexture.c:106: /* bytes are
internally straight, however render pipeline seems to expect premul */
Texture filtering indeed must be premul, it's not just that the render
pipeline expects it, it's the only way to do correct interpolation of
RGBA pixels.

ibuf_get_color_clip should get the same modification.

https://codereview.appspot.com/7018048/