The parameter has been deprecated since c851a2ed5ce8.

It now uses custom alloc_aligned() wrapper for all allocations,
therefore all allocations are larger than expected by (64 + sizeof(void*)).
Further, they are seen as allocations of 1 element.  Relevant calculations
were adjusted to reflect this, and state allocation is now protected
with a flag to avoid misinterpreting other allocations as the zlib
deflate_state allocation.

Further, it no longer forces window bits to 13 on compression level 1,
so the comment was adjusted to reflect this.

SSL context is not present if the default server has neither certificates nor
ssl_reject_handshake enabled.  Previously, this led to null pointer dereference
before it would be caught with configuration checks.

Additionally, non-default servers with distinct SSL contexts need to initialize
compatibility layer in order to complete a QUIC handshake.

Since 4611:2b6cb7528409 responses from the gzip static, flv, and mp4 modules
can be used with subrequests, though empty files were not properly handled.
Empty gzipped, flv, and mp4 files thus resulted in "zero size buf in output"
alerts.  While valid corresponding files are not expected to be empty, such
files shouldn't result in alerts.

Fix is to set b->sync on such empty subrequest responses, similarly to what
ngx_http_send_special() does.

Additionally, the static module, the ngx_http_send_response() function, and
file cache are modified to do the same instead of not sending the response
body at all in such cases, since not sending the response body at all is
believed to be at least questionable, and might break various filters
which do not expect such behaviour.

Now "listen" directve has a new "quic" parameter which enables QUIC protocol
for the address.  Further, to enable HTTP/3, a new directive "http3" is
introduced.  The hq-interop protocol is enabled by "http3_hq" as before.
Now application protocol is chosen by ALPN.

Previously used "http3" parameter of "listen" is deprecated.

The change allows to compile QUIC with OpenSSL which lacks BoringSSL QUIC API.

This implementation does not support 0-RTT.

In contrast to on-the-fly gzipping with gzip filter, static gzipped
representation as returned by gzip_static is persistent, and therefore
the same binary representation is available for future requests, making
it possible to use range requests.

Further, if a gzipped representation is re-generated with different
compression settings, it is expected to result in different ETag and
different size reported in the Content-Range header, making it possible
to safely use range requests anyway.

As such, ranges are now allowed for files returned by gzip_static.