This was a workaround to be able to build on case-insensitive file
systems where it might get confused about <string.h> vs <String.h>.
Let's just not support building that way, so String.h can have an
objectively nicer name. :^)
Now there's just CHttpRequest::set_url(URL), no need to specify the
host, port and path manually anymore.
Updated ChanViewer and Downloader for the API change.
