22Call SIP - a stable sip client description

Support audio

Support G.729, Opus, PCMA, PCMU,AMR,AMR-WB,G.722.1,G.722,SPEEX,SPEEX-
WB,iLBC,GSM,ISAC,ISAC-WB codecs.

Support 20-party audio conference.

Support add/modify the SIP message headers.