tls_wrap: proxy handle methods in prototype

Set proxied methods wrappers in `TLSWrap` prototype instead of doing it
on every socket allocation. Should speed up things a bit and will
certainly make heapsnapshot less verbose.

PR-URL: https://github.com/iojs/io.js/pull/1108


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>