Add aligment fix for 4:2 planar video

[Fktor]

Issue: ValveSoftware/Proton#576

[Fktor]

Trying to fix a Resident Evil 0 video issue. The problem is that we have a video in 4:2:0 format, and the uv planes have a width that is not a multiple of 4. Gstreamer forces the stride to be aligned to 4, while the game expects the original stride. This causes visual green/red line artifacts.

I've attached the fix to a NV12 fix that was already present since they're from the same family of problems.

First time trying to fix something in Proton, so give it a hard look.

[cmccarthy-codeweavers]

Should be good after some minor fixes. This loop:

        dst = map_info.data + dst_info.offset[plane1];
        src = map_info.data + src_info.offset[plane1];
        for (i = 0; i < aligned_height; ++i)
        {
            memmove(dst, src, dst_info.stride[plane1]);
            dst += dst_info.stride[plane1];
            src += src_info.stride[plane1];
        }

The height is the same for plane 2, so instead of being duplicated for plane2, it can be inside an outer loop: for (plane = 1; plane <=2; ++plane)

else should occur on a new line instead of } else

Extra condition lines are always only double-indented (4 spaces x 2), so it would be:

                fix_yv12 = (GST_VIDEO_INFO_FORMAT(&video_info) == GST_VIDEO_FORMAT_YV12
                        || GST_VIDEO_INFO_FORMAT(&video_info) == GST_VIDEO_FORMAT_I420)
                        && (video_info.stride[1] > GST_ROUND_UP_2(video_info.width/2));

Trace messages should mention I420 too, so it doesn't look like a format snafu occurred, e.g. something like "Enabling the YV12/I420 alignment fix."

I think it should be ok to just call assert(0) instead of GST_ERROR("fix_align called for unsupported format.")

The commit message should be something like:

winegstreamer: HACK: Add alignment fix for 4:2 planar video.