check_http - support TLS v1.2 (#1338)

[Stuart Henderson]

On 2015-09-20, Frank Bulk wrote:
> Also, what do we need to do support HTTP 2.0?

That's quite a bit more complicated than check_http currently has
to handle. I think the best option for this might be a separate check
program using a version of libcurl built with HTTP/2.0 support.
https://github.com/andreasbaumann/nagios-plugin-curl might be a
starting point (or might even be directly usable).