Attended call transfer implementation. The changes involves:
- Added support for SIP Replaces extension (RFC 3891)
- Added pjsua_call_xfer_replaces() to perform attended call
  transfer.
- PJSUA checks and process Replaces header in incoming calls
- Added pjsip_ua_find_dialog() API.
- Added pjsip_endpt_has_capability() API.
- Added pjsip_endpt_send_response2() API.
- etc.



git-svn-id: https://svn.pjsip.org/repos/pjproject/trunk@797 74dad513-b988-da41-8d7b-12977e46ad98
19 files changed