TS-1516: use_client_addr breaks parent proxy configuration

When use_client_addr is configured and a plugin/configuration tells
the ATS to send the transaction to a parent proxy it will try to
connect to the client address.  The parent proxy settings should
override the client IP.
TS-1513: SPDY plugin crashes on connection close

Fix TSVConn double-release on SPDY stream close.
TS-1525: SPDY plugin sends  malformed HTTP version string
Added DNS stats
TS-1526: SNI support breaks IP-based lookup

The OpenSSL SNI callback will revert to the default context if the
name-based lookup fails even if we already did a successful
address-based context lookup. In this case, we clobber the address-based
context with a default context.
TS-1532 esi plugin does not support cookie sub keys

  we implement the cookie sub keys and make test now working.
  also disable the keep-alive
TS-1503 make Event::schedule simple and efficient.
TS-1501 vc`s inactivity_timeout event should be schedule in vc`s thread
TS-1534: implement the interim cache for ESI parser result
TS-1535: FetchSM process_fetch_write should ignore event TS_EVENT_VCONN_WRITE_READY
SPDY: Use TSIOBufferReaderStart where appropriate
TS-1539: Update build package list in README
pkgconfig is spelt pkconf on BSD
Format size_t with %zu
Log the number of directory bytes allocated
Format off_t as long long
header_rewrite - added license info
TS-1446: Make sure age header is enabled.

The RFC dictates that we must enable the age header if we are returning stale
content. This has been overridable since e24e79d. This now just makes sure
we do this when serving stale content.
TS-1542: Fix so that rfc5861 plugin will compile against older versions of TS.
SDK man pages TSAPI, TSDebug, TSMalloc, TSTrafficServerVersion