Fixed setting proposed streams on hold when holding during a re-INVITE

Ignore-this: 67c916ca8779fa72d4211a01d06ca6dd

darcs-hash:20140307111027-56b4d-ed714c7e04ba307ddb2979765c28c4760498bd31
Fix originator for SIPSessionProposalRejected

Ignore-this: c4fb258b4dffa711dad7e7e8ec434dcf

In SIPSessionProposalAccepted/Rejected, originator refers to who initiated
the proposal.

darcs-hash:20140312130620-56b4d-e1eb52061a63830a928d5ab0219df7ada8a2935e