Curl and libcurl 7.52.0

 Public curl releases:         161
 Command line options:         187
 curl_easy_setopt() options:   225
 Public functions in libcurl:  61
 Contributors:                 1467

This release includes the following changes:

 o nss: map CURL_SSLVERSION_DEFAULT to NSS default
 o vtls: support TLS 1.3 via CURL_SSLVERSION_TLSv1_3
 o curl: introduce the --tlsv1.3 option to force TLS 1.3
 o curl: Add --retry-connrefused [11]

This release includes the following bugfixes:

 o msvc: removed a straggling reference to strequal.c
 o winbuild: remove strcase.obj from curl build [1]
 o examples: bugfixed multi-uv.c
 o configure: verify that compiler groks -Werror=partial-availability [2]
 o mbedtls: fix build with mbedtls versions < 2.4.0 [3]
 o dist: add unit test CMakeLists.txt to the tarball
 o curl -w: added more decimal digits to timing counters [4]
 o easy: Initialize info variables on easy init and duphandle [5]
 o cmake: disable poll for macOS [6]
 o http2: Don't send header fields prohibited by HTTP/2 spec [7]
 o ssh: check md5 fingerprints case insensitively (regression) [8]
 o openssl: initial TLS 1.3 adaptions
 o curl_formadd.3: *_FILECONTENT and *_FILE need the file to be kept
 o printf: fix ".*f" handling [9]
 o examples/fileupload.c: fclose the file as well
 o SPNEGO: Fix memory leak when authentication fails [10]
 o realloc: use Curl_saferealloc to avoid common mistakes [12]
 o openssl: make sure to fail in the unlikely event that PRNG seeding fails
 o URL-parser: for file://[host]/ URLs, the [host] must be localhost [13]

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:

  Adam Piggott, Andrei Sedoi, Bruce Stephens, Dan Fandrich, Daniel Hwang,
  Daniel Stenberg, Frank Gevaerts, Isaac Boukris, Jakub Zakrzewski,
  Kamil Dudka, Mauro Rappa, Mike Crowe, Neal Poole, Peter Wu, Ray Satiro,
  Ricki Hirner, Tatsuhiro Tsujikawa, Tony Kelman,
  (18 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=1098
 [2] = https://curl.haxx.se/bug/?i=1104
 [3] = https://curl.haxx.se/bug/?i=1087
 [4] = https://curl.haxx.se/bug/?i=1106
 [5] = https://curl.haxx.se/bug/?i=1103
 [6] = https://curl.haxx.se/bug/?i=1089
 [7] = https://curl.haxx.se/bug/?i=1092
 [8] = https://github.com/curl/curl/commit/ce8d09483eea2fcb1b50e323e1a8ed1f3613b2e3#commitcomment-19666146
 [9] = https://curl.haxx.se/bug/?i=1113
 [10] = https://curl.haxx.se/bug/?i=1115
 [11] = https://curl.haxx.se/bug/?i=1064
 [12] = https://curl.haxx.se/mail/lib-2016-11/0087.html
 [13] = https://curl.haxx.se/mail/lib-2016-11/0104.html