TLS SNI - add low level support for SNI to the networking code

TLS SNI - add low level support for SNI to the networking code

This commit adds support for setting SNI hostnames in outgoing
connections over TLS.

Most of the changes are related to either adapting the code to accept
and extra argument in *connect() functions and a couple of changes to
the TLS Stream to actually make use of the new SNI hostname
information.

(cherry picked from commit 6691a1530d976c36133166662d7291fe63e1ef83)