Enable HTTPv3 protocol by default.
Remove third-party clojure module due to a build issue.
The OpenSSL compatibility layer, which emulates BoringSSL
QUIC API for OpenSSL, is enabled by default, and 0-RTT is
not supported in this mode.
Alternativly, it's possible to build nginx with a third-party
library from ports tree, that provides QUIC support:
o) BoringSSL
o) LibreSSL
o) QuicTLS
<Changelog>
*) Feature: experimental HTTP/3 support.
</Changelog>
