Varnish 4.1 to HTTP/S backend

[Dridi Boukelmoune]

> Unfortunately not. It should be possible to write a https VMOD now, it might be quite cumbersome to write (the internal APIs are not all in place) but nobody has picked up the glove (yet). If I recall correctly you might not be able to reuse the internal HTTP client inside varnishd when writing the VMOD which means you'll have to use an external https capable library and redo a lot of the backend semantics. But I haven't looked into this in a while so take all this with a grain of salt. If somebody know more I'm sure I'll be corrected or confirmed.

Sounds accurate to me. It can be done but it's a lot of work partly
because we can't reuse the native HTTP backends.