Previously this would lead to an abort for an empty path (`/`), because
`http:/` cannot be parsed correctly.
The URI becomes the `target` in `request`, so it seems best to add the
`Host` header value too.
Note that this is still not 100% correct:
HTTP headers are case-insensitive, so it could also be `host:` or `HoSt`.
Right now headers are not normalized.
However it will not abort if `Host` is missing:
In that case `header_get` returns an empty string and then `http:///`
(three slashes) is parsed with an empty host name as expected.
Jan-Erik Rediger
