Pending RELEASE-NOTES for the upcoming release

This is work in progress and will change before the release goes public on 21st of July 2021.

Changes:

• CURLE_SETOPT_OPTION_SYNTAX: new error name for wrong setopt syntax
• hostip: make 'localhost' return fixed values
• mbedtls: add support for cert and key blob options
• metalink: remove
• mqtt: add support for username and password

Bugfixes:

• ares: always store IPv6 addresses first
• asyn-ares: remove check for 'data' in Curl_resolver_cancel
• bearssl: explicitly initialize all fields of Curl_ssl
• bearssl: remove incorrect const on variable that is modified
• c-hyper: abort CONNECT response reading early on non 2xx responses
• c-hyper: clear NTLM auth buffer when request is issued
• c-hyper: convert HYPERE_INVALID_PEER_MESSAGE to CURLE_UNSUPPORTED_PROTOCOL
• c-hyper: fix NTLM on closed connection tested with test159
• c-hyper: fix the uploaded field in progress callbacks
• c-hyper: handle NULL from hyper_buf_copy()
• c-hyper: support CURLINFO_STARTTRANSFER_TIME
• c-hyper: support CURLOPT_HEADER
• ccsidcurl: fix the compile errors
• CI: add Circle CI
• CI: add jobs using Zuul
• cmake: add CURL_DISABLE_NTLM option
• cmake: avoid leaking absolute paths into exported config
• cmake: try well-known send/recv signature for Apple
• configure: add --disable-ntlm option
• configure: disable RTSP when hyper is selected
• configure: rename get-easy-option configure option to get-easy-options
• conn_shutdown: if closed during CONNECT cleanup properly
• conncache: lowercase the hash key for better match
• cookies: track expiration in jar to optimize removals
• curl: ignore blank --output-dir
• Curl_ntlm_core_mk_nt_hash: fix OOM in error path
• Curl_ssl_getsessionid: fail if no session cache exists
• CURLOPT_WRITEFUNCTION.3: minor update of the example
• docs/INSTALL: remove mentions of configure --with-darwin-ssl
• docs: use --max-redirs instead of --max-redir
• doh: fix wrong DEBUGASSERT for doh private_data
• filecheck: quietly remove test-place/*~
• GHA: add a linux-hyper job
• GHA: add several libcurl tests to the hyper job
• GHA: run the newly fixed tests with hyper
• github: timeout jobs on macOS after 90 minutes
• GOVERNANCE: add 'user', 'committer' and 'contributor'
• hostip: bad CURLOPT_RESOLVE syntax now returns error
• hsts: ignore numberical IP address hosts
• HSTS: not experimental anymore
• http2: clarify 'Using HTTP2' verbose message
• http2: init recvbuf struct for pushed streams
• http2_connisdead: handle trailing GOAWAY better
• http_proxy: deal with non-200 CONNECT response with Hyper
• HYPER: remove mentions of deprecated development branch
• lib: don't compare fd to FD_SETSIZE when using poll
• mbedtls: make mbedtls_strerror always work
• mqtt: detect illegal and too large file size
• multi: add scan-build-6 work-around in curl_multi_fdset
• netrc: skip 'macdef' definitions
• ngtcp2: disable TLSv1.3 compatible mode when using GnuTLS
• openssl: don't remove session id entry in disassociate
• Revert "c-hyper: handle body on HYPER_TASK_EMPTY"
• runtests: also find the last test in Makefile.inc
• runtests: enable 'hyper mode' only for HTTP tests
• runtests: init $VERSION to avoid warnings when using -l
• runtests: parse data/Makefile.inc instead of using make
• runtests: skip disabled tests unless -f is used
• rustls: remove native_roots fallback
• schannel: set ALPN length correctly for HTTP/2
• setopt: fix incorrect comments
• socketpair: fix potential hangs
• ssl: read pending close notify alert before closing the connection
• sws: malloc request struct instead of using stack
• test1216: adjusted for hyper mode
• test1218: adjusted for hyper mode
• test1230: adjust to work in hyper mode
• test1340/1341: adjusted for hyper mode
• test1438/1457: add HTTP keyword to make hyper mode work
• test1594/1595/1596: fix to work in hyper mode
• test269: disable for hyper
• test3010: work with hyper mode
• test328: avoid a header-looking body to make hyper mode work
• test339: CRLFify better to work in hyper mode
• test347: CRLFify to work in hyper mode
• test393: make Content-Length fit within 64 bit for hyper
• test394: hyper returns a different error
• test395: hyper cannot work around > 64 bit content-lengths like built-in
• test433: adjust for hyper mode
• test434: add HTTP keyword
• test500: adjust to work with hyper mode
• test566: adjust to work with hyper mode
• test599: adjusted to work in hyper mode
• test644: remove as duplicate of test 587
• tests: fix Accept-Encoding strips to work with Hyper builds
• travis: add bearssl build
• travis: delete --enable-hsts option (it is the default now) [ci skip]
• travis: remove the arm job
• travis: remove the hyper build
• url.c: remove two variable assigns that are never read
• url: bad CURLOPT_CONNECT_TO syntax now returns error
• vtls: exit addsessionid if no cache is inited
• warnless: simplify type size handling
• Win32: fix build with Watt-32
• winbuild/README: VC should be set to 6 'or larger'

Contributors:

Albin Vass, Alexis Vachette, Alex Xu, Bastian Krause, Christian Weisgerber, Christoph M. Becker, Dan Fandrich, Daniel Gustafsson, Daniel Stenberg, David Hu, Dmitry Karpov, Dmitry Kostjuchenko, Douglas R. Reno, Ebe Janchivdorj, Fawad Mirza, Gabriel Simmer, Gealber Morales, Gergely Nagy, Gisle Vanem, Gregor Jasny, Harry Sintonen, Hugh Macdonald, Jacob Hoffman-Andrews, Joel Depooter, Jon Rumsey, Jun-ya Kato, Kevin Burke, Laurent Dufresne, Marc Hörsken, Mark Swaanenburg, Michael Forney, Michael Kaufmann, Mohammed Naser, nian6324 on github, Paul Groke, Phil E. Taylor, Ray Satiro, Shikha Sharma, Vadim Grinshpun, Viktor Szakats, Zhang Xiuhua,