This API change forces all creation of BUrlRequest to be done via
BUrlProtocolRoster::MakeRequest(). This allows the structure of protocol
addons to be altered without breaking ABI for client applications.
Change-Id: I1785c9136c50d19eaa9e57cb9d259ed8d88a5b56
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3080
Reviewed-by: waddlesplash <waddlesplash@gmail.com>