Updated information: we added recently a workaround to the utf8 downcase function, by moving code already present out of the ICU #if block.
This workaround delegates to the ascii downcase when the string has only codepoints in the ascii range (the way used to do that check is debatable, must be revisited during strings pdd work). Extend it to codepoints in the iso-8859-1 range is not so easy, will need to check the string content. Attempt to transcode will be not helpful if the transcode function used also require ICU.
