nua_stack.c: keep reference when destroying un-ACKed INVITE
nua_stack.c: keep reference when destroying un-ACKed INVITE

darcs-hash:20080912162518-db55f-878c81d8ec61517e652cd33675685951a11a1469.gz

xhook/sofia-sip,erdincay/sofia-sip,xhook/sofia-sip,unispeech/sofia-sip,unispeech/sofia-sip,unispeech/sofia-sip,unispeech/sofia-sip,BelledonneCommunications/sofia-sip,erdincay/sofia-sip,BelledonneCommunications/sofia-sip,jart/sofia-sip,BelledonneCommunications/sofia-sip,erdincay/sofia-sip,jart/sofia-sip,erdincay/sofia-sip,xhook/sofia-sip,BelledonneCommunications/sofia-sip,jart/sofia-sip,xhook/sofia-sip,xhook/sofia-sip