[API REVIEW] SSL support extensions

[Susan Hinrichs]

This was discussed a couple weeks back and some changes made in 
response.   Here it is again in the proper form.  Would like to get this 
merged up now that 5.1 is wrapping up.

JIRA ticket https://issues.apache.org/jira/browse/TS-3006 and related 
ticket https://issues.apache.org/jira/browse/TS-2956

Motivation:  We need to enhance plugin support for SSL processing. 
Specifically need to give plugins the ability to add to the SNI callback 
and the ability to insert code to be executed after the TCP connection 
has completed but before the SSL handshake processing has started.  Also 
added support for a TS_SSL_HOOK_OP_TUNNEL to enable more granular 
decision making on  blind tunneling of SSL connections.

More details, the specific signatures, semantics, and references to 
example plugins are at 
http://network-geographics.com/ats/docs/ssl-api.en.html.

The current implementation is at 
https://github.com/shinrich/trafficserver/tree/ts-3006

Thanks,
Susan