nua_session.c: use signed ss_sdp_version (soa_get_user_version() returns int)
nua_session.c: use signed ss_sdp_version (soa_get_user_version() returns int)

darcs-hash:20081127120944-db55f-b3b4b9e1a149cf56fbd0d86ccfc52094eedec56a.gz

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