Off hand I think it would be fine, and more consistent, for readelf to
display DW_LANG_foo as exactly foo and be done with it. I'm not sure we
have a demonstrated need for the "description" variant at all.
In a similar vein, I don't think "unknown_lang_%#x" and the like make
sense. Just use plain %#x. The context should always make clear what kind
of constant it is.
Thanks,
Roland