Curl and libcurl 7.51.0

 Public curl releases:         160
 Command line options:         185
 curl_easy_setopt() options:   224
 Public functions in libcurl:  61
 Contributors:                 1445

This release includes the following changes:

 o nss: additional cipher suites are now accepted by CURLOPT_SSL_CIPHER_LIST
 o New option: CURLOPT_KEEP_SENDING_ON_ERROR [10]

This release includes the following bugfixes:

 o openssl: fix per-thread memory leak usiong 1.0.1 or 1.0.2 [1]
 o http: accept "Transfer-Encoding: chunked" for HTTP/2 as well [2]
 o LICENSE-MIXING.md: update with mbedTLS dual licensing [3]
 o examples/imap-append: Set size of data to be uploaded [4]
 o test2048: fix url
 o darwinssl: disable RC4 cipher-suite support
 o CURLOPT_PINNEDPUBLICKEY.3: fix the AVAILABILITY formatting
 o openssl: don’t call CRYTPO_cleanup_all_ex_data [5]
 o libressl: fix version output [6]
 o easy: Reset all statistical session info in curl_easy_reset [7]
 o curl_global_cleanup.3: don't unload the lib with sub threads running [8]
 o dist: add CurlSymbolHiding.cmake to the tarball
 o docs: Remove that --proto is just used for initial retrieval [9]
 o configure: Fixed builds with libssh2 in a custom location
 o curl.1: --trace supports % for sending to stderr!
 o cookies: same domain handling changed to match browser behavior [11]
 o formpost: trying to attach a directory no longer crashes [12]

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:

  Akshay Vernekar, Alexander Sinditskiy, Bernard Spil, Dan Fandrich,
  Daniel Gustafsson, Daniel Stenberg, Jeroen Ooms, Kamil Dudka,
  lukaszgn on github, Michael Kaufmann, Nick Zitzmann, Ray Satiro,
  Sebastian Mundry, Sergei Kuzmin, Stephen Brokenshire, Toby Peterson,
  Todd Short, 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=964
 [2] = https://curl.haxx.se/bug/?i=1013
 [3] = https://curl.haxx.se/bug/?i=1019
 [4] = https://curl.haxx.se/bug/?i=1011
 [5] = https://curl.haxx.se/mail/lib-2016-09/0045.html
 [6] = https://curl.haxx.se/bug/?i=1029
 [7] = https://curl.haxx.se/bug/?i=1017
 [8] = https://curl.haxx.se/bug/?i=997
 [9] = https://curl.haxx.se/bug/?i=1031
 [10] = https://curl.haxx.se/libcurl/c/CURLOPT_KEEP_SENDING_ON_ERROR.html
 [11] = https://curl.haxx.se/bug/?i=1050
 [12] = https://curl.haxx.se/bug/?i=1053