(url->string url or http-url) -> string
Accepts either a <url> or <http-url>, and returns it as a string in the usual format.
Examples:
>> a :: [url "http" "www.ephemeralsecurity.com" "/mosvm" #f #f] >> b :: [http-url #f "www.ephemeralsecurity.com" 80 () #f #f] >> (url->string a) :: "http://www.ephemeralsecurity.com/mosvm" >> (url->string b) :: "http://www.ephemeralsecurity.com:80"