Rotation in image Exif data not parsed

[Karl Berry]

    mc> add a package option to graphicx that forces it to run extractbb
    on every image, then apply the extracted rotation to each image. The
    xdvipdfmx driver already does this [...]

Let me just mention that this approach also has the advantage of making
the new conditional for whether to use exif rotation be at the LaTeX
level, without needing any changes to the engines. That sounds like a
massive win to me.

    But I doubt that anyone wants to write an Exif parser in WEB,

For the record, there is some exif-reading stuff in
pdftexdir/writejpg.c. But I think the Lua script approach is better, as
outlined. --thanks, karl.