nua/outbound.c: calculate the keepalive timer interval with regard to the maximum defer interval
nua/outbound.c: calculate the keepalive timer interval with regard to the maximum defer interval

The point is not to miss the keepalive deadlines.

Re-recorded 20090123142528-5b6ca-43c4952962c9ce02469f01ee7bd51b0528ea7a22

darcs-hash:20090128183201-5b6ca-0012003d9a33046c6f070094b0dc1a9470f38aef.gz

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