The "http_header" event now has an "original_name" parameter that allows
access to the original header name (the "name" parameter reamins the
same as before: it's the uppercased header name).
The "mime_header_rec" record type now also includes an "original_name"
field to similarly provide access to original header name in the
following events: "http_all_headers", "mime_one_header", and
"mime_all_headers".