Added test for call hold.
Added test for call hold.

darcs-hash:20051012181958-65a35-12211486184a4c24b428701a29ebeb45e0f33856.gz

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