Major Description
1) Introduce extended FetchSM APIs, which will be used by SPDY.
2) Make TSFetchUrl() dechunk encoding automatically:
If you use TSFetchUrl() to fetch a resource and the response comes back with chunked encoding, you are basically hosed. The caller never gets the SUCCESS event because FetchSM does not know how to decode the body. There's no content-length header and the origin server doesn't drop the TCP connection, so we just sit there waiting for the response to finish forever (well until the origin server drops the connection 10s later).
