GIF loader was completely failing when encountering errors with frame descriptors or individual frames, even when some frames were successfully loaded. Now we attempt to decode at least some frames and fail only when no frames can be decoded at all.
This commit removes the fast_u32_fill and fast_u32_copy functions, as they were only used in one place, and are not optimal.
We actually include what we use where we use it. This change aims to improve the speed of incremental builds.