curl and libcurl 7.66.0

 Public curl releases:         185
 Command line options:         224
 curl_easy_setopt() options:   269
 Public functions in libcurl:  80
 Contributors:                 1991

This release includes the following changes:

 o curl: support parallel transfers with -Z [4]

This release includes the following bugfixes:

 o HTTP3: initial (experimental still not working) support [5]
 o HTTP: use chunked Transfer-Encoding for HTTP_POST if size unknown [10]
 o alt-svc: more liberal ALPN name parsing [17]
 o altsvc: with quiche, use the quiche h3 alpn string [16]
 o appveyor: pass on -k to make
 o asyn-thread: create a socketpair to wait on [14]
 o cleanup: remove the 'numsocks' argument used in many places [25]
 o curl.h: fix outdated comment [23]
 o curl: cap the maximum allowed values for retry time arguments [13]
 o curl: remove outdated comment [24]
 o curl_version_info: provide nghttp2 details [2]
 o docs/MANUAL.md: converted to markdown from plain text [3]
 o easy: resize receive buffer on easy handle reset [9]
 o examples: Avoid reserved names in hiperfifo examples [8]
 o getenv: support up to 4K environment variable contents on windows [21]
 o http2_recv: trigger another read when the last data is returned [11]
 o http_negotiate: improve handling of gss_init_sec_context() failures [18]
 o md4: Use our own MD4 when no crypto libraries are available [15]
 o multi: call detach_connection before Curl_disconnect [6]
 o plan9: add support for running on Plan 9 [22]
 o progress: reset download/uploaded counter between transfers [12]
 o quiche: use the proper HTTP/3 ALPN
 o readwrite_data: repair setting the TIMER_STARTTRANSFER stamp [26]
 o source: remove names from source comments [1]
 o src/makefile: fix uncompressed hugehelp.c generation [19]
 o ssh-libssh: do not specify O_APPEND when not in append mode [7]
 o timediff: make it 64 bit (if possible) even with 32 bit time_t [20]
 o url: make use of new HTTP version if alt-svc has one [16]

This release includes the following known bugs:

 o see docs/KNOWN_BUGS (https://curl.haxx.se/docs/knownbugs.html)

This release would not have looked like this without help, code, reports and
advice from friends like these:

  Alessandro Ghedini, Amit Katyal, Balazs Kovacsics, Brad Spencer,
  Daniel Gustafsson, Daniel Stenberg, Felix Hädicke, Gergely Nagy,
  Ironbars13 on github, Jason Lee, Jonathan Cardoso Machado, Kamil Dudka,
  Kyohei Kadota, Lance Ware, Marcel Raad, Michael Lee, Michal Čaplygin,
  niallor on github, Ray Satiro, Steve Holme, The Infinnovation team,
  Tom van der Woerdt,
  (22 contributors)

        Thanks! (and sorry if I forgot to mention someone)

References to bug reports and discussions on issues:

 [1] = https://curl.haxx.se/bug/?i=4129
 [2] = https://curl.haxx.se/bug/?i=4121
 [3] = https://curl.haxx.se/bug/?i=4131
 [4] = https://curl.haxx.se/bug/?i=3804
 [5] = https://curl.haxx.se/bug/?i=3500
 [6] = https://curl.haxx.se/bug/?i=4144
 [7] = https://curl.haxx.se/bug/?i=4147
 [8] = https://curl.haxx.se/bug/?i=4153
 [9] = https://curl.haxx.se/bug/?i=4143
 [10] = https://curl.haxx.se/bug/?i=4138
 [11] = https://curl.haxx.se/bug/?i=4043
 [12] = https://curl.haxx.se/bug/?i=4084
 [13] = https://curl.haxx.se/bug/?i=4166
 [14] = https://curl.haxx.se/bug/?i=4157
 [15] = https://curl.haxx.se/bug/?i=3780
 [16] = https://curl.haxx.se/bug/?i=4183
 [17] = https://curl.haxx.se/bug/?i=4182
 [18] = https://curl.haxx.se/bug/?i=3992
 [19] = https://curl.haxx.se/bug/?i=4176
 [20] = https://curl.haxx.se/bug/?i=4165
 [21] = https://curl.haxx.se/bug/?i=4174
 [22] = https://curl.haxx.se/bug/?i=3701
 [23] = https://curl.haxx.se/bug/?i=4167
 [24] = https://curl.haxx.se/bug/?i=4172
 [25] = https://curl.haxx.se/bug/?i=4169
 [26] = https://curl.haxx.se/bug/?i=4136