Implement RFC3326 (The Reason Header Field ...).
Implement RFC3326 (The Reason Header Field ...).

Incompatibility notes :

This commit changes (adds arguments) to signals sent between
  - transaction layer and servertransaction :
      {cancelled} -> {cancelled, ExtraHeaders}
  - server transaction and it's parent (sippipe or appserver_glue) :
      {servertransaction_cancelled, ServerHandlerPid} ->
      {servertransaction_cancelled, ServerHandlerPid, ExtraHeaders}
  - appserver_glue and sipproxy :
      {cancel_pending} -> {cancel_pending, EH} (EH = ExtraHeaders)

Cancel-signals sent to client transactions ({cancel, Msg, EH}) were already
prepared for this change and did not have to change.


git-svn-id: 3f662d0c7823f96a484d6a9a7c90f2d7866b6747@1058 e454d3dc-12ff-0310-9b8b-94264392205f

bernardd/yxa,bernardd/yxa,bernardd/yxa,bernardd/yxa