Merge commit '2c4573263a97cc80f441824a75d6502ae04292a8' * commit '2c4573263a97cc80f441824a75d6502ae04292a8': SipPhone: revise hangup() in SipCall and SipConnection.
Merge commit '2c4573263a97cc80f441824a75d6502ae04292a8' * commit '2c4573263a97cc80f441824a75d6502ae04292a8': SipPhone: revise hangup() in SipCall and SipConnection.