Motivation for this change

Update curl to the last version in staging branch

• imap: if a FETCH response has no size, don't call write callback
• ftp: UBsan fixup 'pointer index expression overflowed
• failf: skip the sprintf() if there are no consumers
• fuzzer: move to using external curl-fuzzer
• lib/Makefile.m32: allow customizing dll suffixes
• docs: fix typo in curl_mime_data_cb man page
• darwinssl: add support for TLSv1.3
• build: fix --disable-crypto-auth
• lib/config-win32.h: let SMB/SMBS be enabled with OpenSSL/NSS
• openssl: fix build without HAVE_OPAQUE_EVP_PKEY
• strtoofft: Remove extraneous null check
• multi_cleanup: call DONE on handles that never got that
• tests: added flaky keyword to tests 587 and 644
• pingpong: return error when trying to send without connection
• remove_handle: call multi_done() first, then clear dns cache pointer
• mime: be tolerant about setting the same header list twice in a part
• mime: improve unbinding top multipart from easy handle
• mime: avoid resetting a part's encoder when part's contents change
• mime: refuse to add subparts to one of their own descendants
• RTSP: avoid integer overflow on funny RTSP responses
• curl: don't pass semicolons when parsing Content-Disposition
• openssl: enable PKCS12 support for !BoringSSL
• FAQ: s/CURLOPT_PROGRESSFUNCTION/CURLOPT_XFERINFOFUNCTION
• CURLOPT_NOPROGRESS.3: also refer to xferinfofunction
• CURLOPT_XFERINFODATA.3: fix duplicate see also
• test298: verify --ftp-method nowcwd with URL encoded path
• FTP: URL decode path for dir listing in nocwd mode
• smtp_done: fix memory leak on send failure
• ftpserver: support case insensitive commands
• test950; verify SMTP with custom request
• openssl: don't use old BORINGSSL_YYYYMM macros
• setopt: update current connection SSL verify params
• winbuild/BUILD.WINDOWS.txt: mention WITH_NGHTTP2
• curl: reimplement stdin buffering in -F option
• mime: keep "text/plain" content type if user-specified
• mime: fix the content reader to handle >16K data properly
• configure: remove the C++ compiler check
• memdebug: trace send, recv and socket
• runtests: use valgrind for torture as well
• ldap: silence clang warning
• makefile.m32: allow to override gcc, ar and ranlib
• setopt: avoid integer overflows when setting millsecond values
• setopt: range check most long options
• ftp: reject illegal IP/port in PASV 227 response
• mime: do not reuse previously computed multipart size
• vtls: change struct Curl_ssl close' field name to close_one'
• os400: add missing symbols in config file
• mime: limit bas64-encoded lines length to 76 characters
• mk-ca-bundle: Remove URL for aurora
• mk-ca-bundle: Fix URL for NSS

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.