the condition in the previous request was unmet. This is typically a time
  condition set with CURLOPT_TIMECONDITION and was previously not possible to
  reliably figure out. From bug report #2565128
  (http://curl.haxx.se/bug/view.cgi?id=2565128)

to better know and track symbols in earlier libcurl versions

   getaddrinfo() sorts the response list

This isn't a libcurl bug since this is how getaddrinfo() is *supposed* to work!
Apparently you deal with this using the /etc/gai.conf file.

later)

  version 1.1 instead of 1.0 like before. This change also introduces the new
  proxy type for libcurl called 'CURLPROXY_HTTP_1_0' that then allows apps to
  switch (back) to CONNECT 1.0 requests. The curl tool also got a --proxy1.0
  option that works exactly like --proxy but sets CURLPROXY_HTTP_1_0.

  I updated all test cases cases that use CONNECT and I tried to do some using
  --proxy1.0 and some updated to do CONNECT 1.1 to get both versions run.

line and fixed a few typos.

  CURLOPT_SOCKS5_GSSAPI_SERVICE and CURLOPT_SOCKS5_GSSAPI_NEC to allow libcurl
  to do GSS-style authentication with SOCKS5 proxies. The curl tool got the
  options called --socks5-gssapi-service and --socks5-gssapi-nec to enable
  these.

  to set desired block size to use for TFTP transfers instead of the default
  512 bytes.

  They basically offer the same thing the NO_PROXY environment variable only
  offered previously: list a set of host names that shall not use the proxy
  even if one is specified.

  multi_socket interfaces. The work-around for apps is to simply remove the
  easy handle once the time is up. See also:
  http://curl.haxx.se/bug/view.cgi?id=2501457

new and non-standard one

corrupted in ouputs. Another report from Anthony Bryan.

escape these letters what I think is the correct way.

  corrected spellings and more.

  there are servers "out there" that relies on the client doing this broken
  Digest authentication. Apache even comes with an option to work with such
  broken clients.

  The difference is only for URLs that contain a query-part (a '?'-letter and
  text to the right of it).

  libcurl now supports this quirk, and you enable it by setting the
  CURLAUTH_DIGEST_IE bit in the bitmask you pass to the CURLOPT_HTTPAUTH or
  CURLOPT_PROXYAUTH options. They are thus individually controlled to server
  and proxy.

*_socket_all() and *_socket() aren't used at all but only *_socket_action()
is.