[PATCH v2 0/6] MR9348: comctl32/imagelist: Pre-multiply rgb by the alpha channel in add_dib_bits for v6.

[Ziqing Hui (＠zhui)]

We used to do this when drawing the image. But our tests show that for v6,
the image bitmaps have been alpha pre-multiplied before drawing.
So we should do this when adding images.

--
  v2: comctl32/imagelist: Support adding 32bpp images to a non-32bpp image list for v6.
      comctl32/imagelist: Do alpha blending when adding 32bpp images to a non-32bpp image list.
      comctl32/imagelist: Introduce create_dib_section helper.
      comctl32/imagelist: Introduce image_list_color_flag helper.
      comctl32/imagelist: Pre-multiply rgb by the alpha channel in add_dib_bits for v6.
      comctl32/imagelist: Introduce premultiply_alpha_channel helper.

https://gitlab.winehq.org/wine/wine/-/merge_requests/9348