New API for Outgoing Address

[Sudheer Vinukonda <su...@yahoo-inc.com.INVALID>]

There's currently no TS API to retrieve the source address used by the proxy in the outbound connections. 
I would like to add a new TS API that can provide this info - In addition to making it consistent with the API for inbound addresses (where we have TS API for both remote and local addresses), there may be other use cases that need this info (e.g. applying rate limiting on the inbound side based on the ephemeral ports).
tsapi struct sockaddr const* TSHttpTxnOutgoingAddrGet(TSHttpTxn txnp);
Please review and provide comments/suggestions.

Thanks,
Sudheer