I am going to automatically enable HTTP/2 by default in all nginx
daemons. The benefits of HTTP/2 are widely known and the fallback
support for clients that don't have it are taken care of.
That means that the `http2` option in the config will become a noop.
Instead, there will be a new `nohttp2` option that will allow you to
disable HTTP/2 support in case this is needed - mostly if you're running
a site behind a proxy that isn't capable of HTTP/2.
Our apache had HTTP/2 enabled by default for a long time, this brings
nginx on par with this respect.