nsISOAPResponseListener in Firefox 1.5

 This method is invoked when we receive an asynchronous response to 
 a SOAP message. The listener is registered as part of the original
 asynchronous call invocation. 

 @param aResponse The decoded version of the response.  If an
   error occurred transmitting the response, the status field
   of the response will contain an error code.  The last call
   to the listener may contain a null response, which should
   only be interpreted as an error if your call expected more 
   results than it got.  If the service or the transport
   do not know whether to expect more results, then setting
   the last parameter true may only be possible after the
   last response has already been delivered.

 @param aLast True if this is the last call to the listener.

 @return True to make this the last call to the listener, even
   if last was not true.  Calls which expect a single response
   should return true upon receiving that response to avoid
   possibly recieving another callback with a null response
   indicating that the last response was already sent.