URLWRITE URLWRITE Retrieve a URL into a File

Usage

Given a URL and a timeout, attempts to retrieve the URL and write the
contents to a file.  The syntax is

   f = urlwrite(url,filename,timeout)

The timeout is in milliseconds.  Note that the URL must be a complete
spec (i.e., including the name of the resource you wish to retrieve).  So
for example, you cannot use http://www.google.com as a URL, but must 
instead use http://www.google.com/index.html.
