Curl and libcurl 7.53.0

 Public curl releases:         163
 Command line options:         205
 curl_easy_setopt() options:   244
 Public functions in libcurl:  61
 Contributors:                 1496

This release includes the following changes:

 o unix_socket: added --abstract-unix-socket and CURLOPT_ABSTRACT_UNIX_SOCKET [25]
 o CURLOPT_BUFFERSIZE: support enlarging receive buffer [29]

This release includes the following bugfixes:

 o gnutls-random: check return code for failed random
 o openssl-random: check return code when asking for random
 o http: remove "Curl_http_done: called premature" message
 o cyassl: use time_t instead of long for timeout
 o build-wolfssl: Sync config with wolfSSL 3.10
 o ftp-gss: check for init before use
 o configure: accept --with-libidn2 instead [1]
 o ftp: failure to resolve proxy should return that error code
 o curl.1: add three more exit codes
 o docs/ciphers: link to our own new page about ciphers
 o vtls: s/SSLEAY/OPENSSL - fixes multi_socket timeouts with openssl [2]
 o darwinssl: fix iOS build [3]
 o darwinssl: fix CFArrayRef leak [4]
 o cmake: use crypt32.lib when building with OpenSSL on windows [5]
 o curl_formadd.3: CURLFORM_CONTENTSLENGTH not needed when chunked [6]
 o digest_sspi: copy terminating NUL as well [7]
 o curl: fix --remote-time incorrect times on Windows [8]
 o curl.1: several updates and corrections [11]
 o content_encoding: change return code on a failure
 o curl.h: CURLE_FUNCTION_NOT_FOUND is no longer in use
 o docs: TCP_KEEPALIVE start and interval default to 60 [9]
 o darwinssl: --insecure overrides --cacert if both settings are in use [10]
 o TheArtOfHttpScripting: grammar
 o CIPHERS.md: document GSKit ciphers
 o wolfssl: support setting cipher list
 o wolfssl: display negotiated SSL version and cipher
 o lib506: fix build for Open Watcom [12]
 o asiohiper: improved socket handling [13]
 o examples: make the C++ examples follow our code style too
 o tests/sws: retry send() on EWOULDBLOCK [14]
 o cmake: Fix passing _WINSOCKAPI_ macro to compiler [15]
 o smtp: Fix STARTTLS denied error message
 o imap/pop3: don't print response character in STARTTLS denied messages [16]
 o rand: make it work without TLS backing [17]
 o url: fix parsing for when 'file' is the default protocol [18]
 o url: allow file://X:/path URLs on windows again [19]
 o gnutls: check for alpn and ocsp in configure [20]
 o IDN: Use TR46 'non-transitional' for toASCII translations [21]
 o url: Fix NO_PROXY env var to work properly with --proxy option [22]
 o CURLOPT_PREQUOTE.3: takes a struct curl_slist*, not a char* [23]
 o docs: Add note about libcurl copying strings to CURLOPT_* manpages [24]
 o curl: reset the easy handle at --next
 o --next docs: --trace and --trace-ascii are also global
 o --write-out docs: 'time_total' is not always shown with ms precision
 o http: print correct HTTP string in verbose output when using HTTP/2
 o docs: improved language in README.md HISTORY.md CONTRIBUTE.md [26]
 o http2: disable server push if not requested [27]
 o nss: use the correct lock in nss_find_slot_by_name()
 o usercertinmem.c: improve the short description
 o CURLOPT_CONNECT_TO: Fix compile warnings
 o docs: non-blocking SSL handshake is now supported with NSS
 o *.rc: escape non-ASCII/non-UTF-8 character for clarity [28]
 o mbedTLS: fix multi interface non-blocking handshake [30]
 o PolarSSL: fix multi interface non-blocking handshake [31]

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, Anatol Belski, Antoine Aubert, Chris Araman,
  Christian Weisgerber, Chungtsun Li, Dan Fandrich, Daniel Romero,
  Daniel Stenberg, Dan Jacobson, ERAMOTO Masaya, Fahim Chandurwala,
  Frank Gevaerts, Gisle Vanem, Isaac Boukris, Jiří Malák, John Kohl,
  Kamil Dudka, Kim Minjoong, Kyselgov E.N, Marcus Hoffmann, Max Khon,
  Michael Kaufmann, Mingliang Zhu, Nick Zitzmann, Patrick Monnerat, Peter Wu,
  Praveen Pvs, Ray Satiro, Richy Kim, Tim Rühsen, Viktor Szakáts,
  (32 contributors)

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

References to bug reports and discussions on issues:

 [1] = https://curl.haxx.se/mail/lib-2016-12/0110.html
 [2] = https://curl.haxx.se/bug/?i=1174
 [3] = https://curl.haxx.se/bug/?i=1172
 [4] = https://curl.haxx.se/bug/?i=1173
 [5] = https://curl.haxx.se/bug/?i=1147
 [6] = https://curl.haxx.se/bug/?i=1013
 [7] = https://curl.haxx.se/bug/?i=1180
 [8] = https://curl.haxx.se/bug/?i=1121
 [9] = https://curl.haxx.se/mail/lib-2017-01/0000.html
 [10] = https://curl.haxx.se/bug/?i=1184
 [11] = https://curl.haxx.se/bug/?i=1190
 [12] = https://curl.haxx.se/bug/?i=1196
 [13] = https://curl.haxx.se/bug/?i=1191
 [14] = https://curl.haxx.se/mail/lib-2017-01/0009.html
 [15] = https://curl.haxx.se/bug/?i=1195
 [16] = https://curl.haxx.se/bug/?i=1203
 [17] = https://curl.haxx.se/mail/lib-2017-01/0055.html
 [18] = https://curl.haxx.se/bug/?i=1124
 [19] = https://curl.haxx.se/bug/?i=1187
 [20] = https://curl.haxx.se/bug/?i=1204
 [21] = https://curl.haxx.se/bug/?i=1207
 [22] = https://curl.haxx.se/bug/?i=1140
 [23] = https://curl.haxx.se/bug/?i=1169
 [24] = https://curl.haxx.se/bug/?i=1169
 [25] = https://curl.haxx.se/bug/?i=1197
 [26] = https://curl.haxx.se/bug/?i=1211
 [27] = https://curl.haxx.se/bug/?i=1160
 [28] = https://curl.haxx.se/bug/?i=1217
 [29] = https://curl.haxx.se/bug/?i=1222
 [30] = https://curl.haxx.se/bug/?i=1223
 [31] = https://github.com/curl/curl/issues/1174#issuecomment-274018791
