Bug with generating SDP version in origin line (thanks Joel Dodson for the report)

[bennylp]

RFC 3264 mandates that subsequent SDP offer must have version number in SDP origin line incremented by one. This currently is done in PJSUA-LIB, with the update_sdp_version() function.

Upon checking the source codes, turns out this should have been done by the SDP negotiator, hence the update_sdp_version() shouldn't be necessary. Further checking reveals that there was a bug in the INVITE session (sip_inv.c), which doesn't use the correct SDP offer as "fixed" by the negotiator, hence the INVITE session does not produce the correct SDP.

The corresponding ticket for 1.0 branch is #795

[bennylp]

Fixed in r2643:

• the INVITE session now correctly uses the SDP offer "fixed" by the negotiator, hence it will have the correct origin fields.
• removed update_sdp_version() from PJSUA-LIB
• the negotiator now also fixes the session ID of subsequent answer so that it's identical to the previous SDP

[bennylp]

In r2665:

• fixed compilation error on Symbian