TS-2365: configure max TLS record size

The client can decipher the data only once it has received a full
record over SSL. The record size can have significant impact on the
page load time performance of the application. No limitation on
record size means that clients might have to download up to 16KB
of data before starting to process them, whereas very small records
incur a larger overhead due to record framing. The suggestion is
to configure the TLS record size to fit into a single TCP segment,
this can improve page load times on browsers located over high
latency or low bandwidth networks.

ref: http://www.igvita.com/2013/10/24/optimizing-tls-record-size-and-buffering-latency/
TS-2413: release memory for idle SSL connections

OpenSSL tends to allocate about 50KB of memory for each connection.
Setting flag: "SSL_MODE_RELEASE_BUFFERS" can save around 34K per
idle SSL connection. This flag has no effect on SSL v2 connections,
or on DTLS connections.

ref: http://www.openssl.org/docs/ssl/SSL_CTX_set_mode.html
TS-2410: document some of the behavior of TSHttpTxnCacheLookupUrlGet