[reSIProcate] dum shutdown issues (IMPORTANT)

[Jason Fischl]

Scott Godin wrote:

>I like this!  This should make the shutdown procedure much easier on the app
>developers.  
>
>PS.  I agree that dum should own the stack.  We will either need to add a
>new dum::getStack() method and/or dum::addTransport(..) methods.
>
>  
>
I decided to just put in the addTransport methods. Could also publicly 
inherit from SipStack.

Jason