cURL 7.66.0

What's new in this version:

Changes:
- CURLINFO_RETRY_AFTER: parse the Retry-After header value
- HTTP3: initial (experimental still not working) support
- curl: --sasl-authzid added to support CURLOPT_SASL_AUTHZID from the tool
- curl: support parallel transfers with -Z
- curl_multi_poll: a sister to curl_multi_wait() that waits more
- sasl: Implement SASL authorisation identity via CURLOPT_SASL_AUTHZID

Bugfixes:
- CVE-2019-5481: FTP-KRB double-free
- CVE-2019-5482: TFTP small blocksize heap buffer overflow
- CI: remove duplicate configure flag for LGTM.com
- CMake: remove needless newlines at end of gss variables
- CMake: use platform dependent name for dlopen() library
- CURLINFO docs: mention that in redirects times are added
- CURLOPT_ALTSVC.3: use a "" file name to not load from a file
- CURLOPT_ALTSVC_CTRL.3: remove CURLALTSVC_ALTUSED
- CURLOPT_HEADERFUNCTION.3: clarify
- CURLOPT_HTTP_VERSION: seting this to 3 forces HTTP/3 use directly
- CURLOPT_READFUNCTION.3: provide inline example
- CURLOPT_SSL_VERIFYHOST: treat the value 1 as 2
- Curl_addr2string: take an addrlen argument too
- Curl_fillreadbuffer: avoid double-free trailer buf on error
- HTTP: use chunked Transfer-Encoding for HTTP_POST if size unknown
- alt-svc: add protocol version selection masking
- alt-svc: fix removal of expired cache entry
- alt-svc: make it use h3-22 with ngtcp2 as well
- alt-svc: more liberal ALPN name parsing
- alt-svc: send Alt-Used: in redirected requests
- alt-svc: with quiche, use the quiche h3 alpn string
- appveyor: pass on -k to make
- asyn-thread: create a socketpair to wait on
- build-openssl: fix build with Visual Studio 2019
- cleanup: move functions out of url.c and make them static
- cleanup: remove the 'numsocks' argument used in many places
- configure: avoid undefined check_for_ca_bundle
- curl.h: add CURL_HTTP_VERSION_3 to the version enum
- curl.h: fix outdated comment
- curl: cap the maximum allowed values for retry time arguments
- curl: handle a libcurl build without netrc support
- curl: make use of CURLINFO_RETRY_AFTER when retrying
- curl: remove outdated comment
- curl: use .curlrc (with a dot) on Windows
- curl: use CURLINFO_PROTOCOL to check for HTTP(s)
- curl_global_init_mem.3: mention it was added in 7.12.0
- curl_version: bump string buffer size to 250
- curl_version_info.3: mentioned ALTSVC and HTTP3
- curl_version_info: offer quic (and h3) library info
- curl_version_info: provide nghttp2 details
- defines: avoid underscore-prefixed defines
- docs/ALTSVC: remove what works and the experimental explanation
- docs/EXPERIMENTAL: explain what it means and what's experimental now
- docs/MANUAL.md: converted to markdown from plain text
- docs/examples/curlx: fix errors
- docs: s/curl_debug/curl_dbg_debug in comments and docs
- easy: resize receive buffer on easy handle reset
- examples: Avoid reserved names in hiperfifo examples
- examples: add http3.c, altsvc.c and http3-present.c
- getenv: support up to 4K environment variable contents on windows
- http09: disable HTTP/0.9 by default in both tool and library
- http2: when marked for closure and wanted to close == OK
- http2_recv: trigger another read when the last data is returned
- http: fix use of credentials from URL when using HTTP proxy
- http_negotiate: improve handling of gss_init_sec_context() failures
- md4: Use our own MD4 when no crypto libraries are available
- multi: call detach_connection before Curl_disconnect
- netrc: make the code try ".netrc" on Windows
- nss: use TLSv1.3 as default if supported
- openssl: build warning free with boringssl
- openssl: use SSL_CTX_set__proto_version() when available
- plan9: add support for running on Plan 9
- progress: reset download/uploaded counter between transfers
- readwrite_data: repair setting the TIMER_STARTTRANSFER stamp
- scp: fix directory name length used in memcpy
- smb: init *msg to NULL in smb_send_and_recv()
- smtp: check for and bail out on too short EHLO response
- source: remove names from source comments
- spnego_sspi: add typecast to fix build warning
- src/makefile: fix uncompressed hugehelp.c generation
- ssh-libssh: do not specify O_APPEND when not in append mode
- ssh: move code into vssh for SSH backends
- sspi: fix memory leaks
- tests: Replace outdated test case numbering documentation
- tftp: return error when packet is too small for options
- timediff: make it 64 bit (if possible) even with 32 bit time_t
- travis: reduce number of torture tests in 'coverage'
- url: make use of new HTTP version if alt-svc has one
- urlapi: verify the IPv6 numerical address
- urldata: avoid 'generic', use dedicated pointers
- vauth: Use CURLE_AUTH_ERROR for auth function errors