Decodes email headers, so the bytes are split by CRLF (if not part of FWS) and then, for every line the codec
is applied to decode header field.
Decodes email headers, so the bytes are split by CRLF (if not part of FWS) and then, for every line the codec
is applied to decode header field.
Codec to decode header fields
strips any whitespace from start of the bytes supplied *