Remove the vaguely defined plane_bits and component_bits fields from
struct mp_imgfmt_desc. Add weird replacements for existing uses. Remove
the bytes[] field, replace uses with bpp[].
Fix some potential alignment issues in existing code. As a compromise,
split mp_image_pixel_ptr() into 2 functions, because I think it's a bad
idea to implicitly round, but for some callers being slightly less
strict is convenient.
This shouldn't really change anything. In fact, it's a 100% useless
change. I'm just cleaning up what I started almost 8 years ago (see
commit 00653a3eb0). With this I've decided to keep mp_imgfmt_desc,
just removing the weird parts, and keeping the saner parts.
caee8748da