makeurl — construct url's based on hostname, port.
filename?Create a self referencing URL from a filename. makeurl can be used in three ways
Example of absolute path:
::rivet::makeurl /tclp.gif
 returns
		    http://[hostname]:[port]/tclp.gif.
		    where hostname and port are the hostname and port of the
		    server in question. The protocol prefix is inferred from the protocol in the URL referencing the
		    script.