/*
 * call-seq:
 *   field.remote_file = "filename"                   => "filename"
 * 
 * Set the POST field remote filename for this PostField (when performing
 * a file upload). If no remote filename is provided, and no content_proc
 * is supplied, the local filename is used. If no remote filename is 
 * specified when a content_proc is used, an exception will be raised 
 * during the perform. 
 */
static VALUE ruby_curl_postfield_remote_file_set(VALUE self, VALUE remote_file) {