Pending RELEASE-NOTES for the upcoming release

This is work in progress and will change before the release goes public on 10th of November 2021.

Changes:

• CURLOPT_MAXLIFETIME_CONN: maximum allowed lifetime for conn reuse
• CURLOPT_PREREQFUNCTION: add new callback
• libssh2: add SHA256 fingerprint support
• urlapi: add curl_url_strerror()
• urlapi: support UNC paths in file: URLs on Windows
• wolfssl: allow setting of groups/curves

Bugfixes:

• aws-sigv4: make signature work when post data is binary
• BINDINGS: URL updates
• build: remove checks for WinSock 1
• c-hyper: make Curl_http propagate errors better
• c-hyper: use hyper_request_set_uri_parts to make h2 better
• checksrc: ignore preprocessor lines
• CI/makefiles: introduce dedicated test target
• ci: update Lift config to match requirements of curl build
• cirrus: remove FreeBSD 11.4 from the matrix
• cirrus: switch to openldap24-client
• cleanup: constify unmodified static structs
• cmake: add CURL_ENABLE_SSL option
• cmake: with OpenSSL, define OPENSSL_SUPPRESS_DEPRECATED
• cmdline-opts: made the 'Added:' field mandatory
• connect: use sysaddr_un from sys/un.h or custom-defined for windows
• curl-openssl.m4: modify library order for openssl linking
• curl-openssl: pass argument to sed single-quoted
• curl.1: remove mentions of really old version changes
• curl: actually append "-" to --range without number only
• curl: correct grammar in generated libcurl code
• curl: print help descriptions in an aligned right column
• curl_gssapi: fix link error on macOS Monterey
• curl_ntlm_core: use OpenSSL only if DES is available
• CURLOPT_HTTPHEADER.3: add descripion for specific headers
• docs/Makefile.am: repair 'make html'
• doh: remove experimental code for DoH with GET
• examples/htmltidy: correct wrong printf() use
• examples/imap-append: fix end-of-data check
• gen.pl: insert the current date and version in generated man page
• http2: make getsock not wait for write if there's no remote window
• HTTP3: fix the HTTP/3 Explained book link
• http: fix Basic auth with empty name field in URL
• http: remove assert that breaks hyper
• http: set content length earlier
• http_proxy: make hyper CONNECT() return the correct error code
• lib/mk-ca-bundle.pl: skip certs passed Not Valid After date
• lib: avoid fallthrough cases in switch statements
• libcurl.rc: switch out the copyright symbol for plain ASCII
• libssh2: Get the version at runtime if possible
• llist: remove redundant code, branch will not be executed
• maketgz: redirect updatemanpages.pl output to /dev/null
• md5: fix compilation with OpenSSL 3.0 API
• misc: fix a few issues on MidnightBSD
• misc: fix typos in docs and comments
• ngtcp2: fix QUIC transport parameter version
• NTLM: use DES_set_key_unchecked with OpenSSL
• openssl: with OpenSSL 1.1.0+ a failed RAND_status means goaway
• sasl: binary messages
• scripts/delta: count command line options in the new file
• sha256: use high-level EVP interface for OpenSSL
• sws: fix memory leak on exit
• test1185: verify checksrc
• tests: disable test 2043
• tool_cb_prg: make resumed upload progress bar show better
• tool_listhelp: easier generated with gen.pl
• tool_main: fix typo in comment
• url: set "k->size" -1 at start of request
• urlapi: skip a strlen(), pass in zero
• urlapi: URL decode percent-encoded host names
• version_win32: use actual version instead of manifested version
• vtls: Fix a memory leak if an SSL session cannot be added to the cache
• wolfssl: use for SHA256, MD4, MD5, and setting DES odd parity

Contributors:

8U61ife on github, a1346054 on github, Abhinav Singh, Alexander Chuykov, Anthony Hu, beslick5 on github, Bo Anderson, Daniel Gustafsson, Daniel Stenberg, David Cook, Gisle Vanem, Gleb Ivanovsky, h1zzz on github, Harry Sintonen, Hayden Roche, Jakub Zakrzewski, Jan Mazur, Jeffrey Tolar, Joel Depooter, Josip Medved, Jun-ya Kato, Kirill Efimov, Lucas Holt, Marcel Raad, Marc Hörsken, Mats Lindestam, Max Dymond, Michael Afanasiev, Michael Baentsch, Michael Kaufmann, Momoka Yamamoto, Noam Moshe, Patrick Monnerat, Rafał Mikrut, Randall S. Becker, Raul Onitza-Klugman, Ray Satiro, Rick Lane, Rikard Falkeborn, Ryan Mast, Sean Molenaar, Sergey Markelov, sergio-nsk on github, Sharon Brizinov, Stathis Kapnidis, Steini2000 on github, Thomas M. DuBuisson, tlahn on github, Viktor Szakats, Vitaly Varyvdin, Wyatt O'Day, Борис Верховский,