As the list has gotten a little messy and hard to read, especially with
the introduction of deprecated items, aligned the values and comments
into clean columns and reworked some of the comments in the process.

Support for Kerberos V4 was removed in v7.33.0.

Option --pinnedpubkey takes a path to a public key in DER format and
only connect if it matches (currently only implemented with OpenSSL).

Provides CURLOPT_PINNEDPUBLICKEY for curl_easy_setopt().

Extract a public RSA key from a website like so:
openssl s_client -connect google.com:443 2>&1 < /dev/null | \
sed -n '/-----BEGIN/,/-----END/p' | openssl x509 -noout -pubkey \
| openssl rsa -pubin -outform DER > google.com.der

Each backend now defines CURL_SSL_BACKEND accordingly. Added the *AXTLS
one which was missing previously.

Removing defines, even obsolete ones that haven't been used for a very
long time, still break a lot of applications.

Bug: https://github.com/bagder/curl/pull/106

1 - fixes the warnings when built without http2 support

2 - adds CURLE_HTTP2, a new error code for errors detected by nghttp2
basically when they are about http2 specific things.

- Replace CURLAUTH_GSSNEGOTIATE with CURLAUTH_NEGOTIATE
- CURL_VERSION_GSSNEGOTIATE is deprecated which
  is served by CURL_VERSION_SSPI, CURL_VERSION_GSSAPI and
  CURUL_VERSION_SPNEGO now.
- Remove display of feature 'GSS-Negotiate'

This is consistent with the existing obsolete error code naming
convention.

... from the CINIT() enum

We now provide the "real" names in the CINIT() macro setup for CURLOPT_*
symbols, and we provide backwards compatibility defines for the old
symbols as defines instead of vice versa.

This allows us to better use the CINIT() list to check for existing and
current option names.

Modified the logic so that CURLOPT_HEADEROPT now controls if PROXYHEADER
is actually used or not.

Includes docs and new test cases: 1525, 1526 and 1527

Co-written-by: Vijay Panghal

Replaced the #define CURL_TIMEOUT_EXPECT_100 in transfer.c with the
CURLOPT_EXPECT_100_TIMEOUT_MS option to make the timeout configurable.

when using --http2 one can now selectively disable NPN or ALPN with
--no-alpn and --no-npn. for now honored with NSS only.

TODO: honor this option with GnuTLS and OpenSSL

To avoid the regression when users pass in passwords containing semi-
colons, we now drop the ability to set the login options with the same
options. Support for login options in CURLOPT_USERPWD was added in
7.31.0.

Test case 83 was modified to verify that colons and semi-colons can be
used as part of the password when using -u (CURLOPT_USERPWD).

Bug: http://curl.haxx.se/bug/view.cgi?id=1311


Reported-by: Petr Bahula
Assisted-by: Steve Holme
Signed-off-by: Daniel Stenberg <daniel@haxx.se>

curl.h should also include <sys/select.h> on OpenBSD to reliably
pull in select().  Typically, including <sys/time.h> will be enough,
but not if strict standards-compliance is requested (e.g. by defining
_XOPEN_SOURCE).

1) Renamed curl_tlsinfo to curl_tlssessioninfo as discussed on the
mailing list.
2) Renamed curl_ssl_backend to curl_sslbackend so it doesn't follow our
function naming convention.
3) Updated sessioninfo.c example accordingly.

Added new API for returning a SSL backend type and pointer, in order to
allow access to the TLS internals, that may then be used to obtain X509
certificate information for example.

Rather than set the authentication options as part of the login details
specified in the URL, or via the older CURLOPT_USERPWD option, added a
new libcurl option to allow the login options to be set separately.

CURL_SSLVERSION_TLSv1_0, CURL_SSLVERSION_TLSv1_1,
CURL_SSLVERSION_TLSv1_2 enum values are added to force exact TLS version
(CURL_SSLVERSION_TLSv1 means TLS 1.x).

axTLS:
axTLS only supports TLS 1.0 and 1.1 but it cannot be set that only one
of these should be used, so we don't allow the new enum values.

darwinssl:
Added support for the new enum values.

SChannel:
Added support for the new enum values.

CyaSSL:
Added support for the new enum values.
Bug: The original CURL_SSLVERSION_TLSv1 value enables only TLS 1.0 (it
did the same before this commit), because CyaSSL cannot be configured to
use TLS 1.0-1.2.

GSKit:
GSKit doesn't seem to support TLS 1.1 and TLS 1.2, so we do not allow
those values.
Bugfix: There was a typo that caused wrong SSL versions to be passed to
GSKit.

NSS:
TLS minor version cannot be set, so we don't allow the new enum values.

QsoSSL:
TLS minor version cannot be set, so we don't allow the new enum values.

OpenSSL:
Added support for the new enum values.
Bugfix: The original CURL_SSLVERSION_TLSv1 value enabled only TLS 1.0,
now it enables 1.0-1.2.

Command-line tool:
Added command line options for the new values.

It isn't added as a separate protocol as HTTP2 will be done over HTTP://
URLs that can be upgraded to HTTP2 if the server supports it as well.

Initial library considerations documented in lib/README.http2

Added the ability to specify an XOAUTH2 bearer token [RFC6750] via the
option CURLOPT_XOAUTH2_BEARER for authentication using RFC6749 "OAuth
2.0 Authorization Framework".

Renamed to "enum curl_khtype" now. Will break compilation for programs
that rely on the enum name.

Bug: https://github.com/bagder/curl/pull/76
Reported-by: Shawn Landden

CURLOPT_XFERINFOFUNCTION is now the preferred progress callback function
and CURLOPT_PROGRESSFUNCTION is considered deprecated.

This new callback uses pure 'curl_off_t' arguments to pass on full
resolution sizes. It otherwise retains the same characteristics: the
same call rate, the same meanings for the arguments and the return code
is used the same way.

The progressfunc.c example is updated to show how to use the new
callback for newer libcurls while supporting the older one if built with
an older libcurl or even built with a newer libcurl while running with
an older.

Introducing a number of options to the multi interface that
allows for multiple pipelines to the same host, in order to
optimize the balance between the penalty for opening new
connections and the potential pipelining latency.

Two new options for limiting the number of connections:

CURLMOPT_MAX_HOST_CONNECTIONS - Limits the number of running connections
to the same host. When adding a handle that exceeds this limit,
that handle will be put in a pending state until another handle is
finished, so we can reuse the connection.

CURLMOPT_MAX_TOTAL_CONNECTIONS - Limits the number of connections in total.
When adding a handle that exceeds this limit,
that handle will be put in a pending state until another handle is
finished. The free connection will then be reused, if possible, or
closed if the pending handle can't reuse it.

Several new options for pipelining:

CURLMOPT_MAX_PIPELINE_LENGTH - Limits the pipeling length. If a
pipeline is "full" when a connection is to be reused, a new connection
will be opened if the CURLMOPT_MAX_xxx_CONNECTIONS limits allow it.
If not, the handle will be put in a pending state until a connection is
ready (either free or a pipe got shorter).

CURLMOPT_CONTENT_LENGTH_PENALTY_SIZE - A pipelined connection will not
be reused if it is currently processing a transfer with a content
length that is larger than this.

CURLMOPT_CHUNK_LENGTH_PENALTY_SIZE - A pipelined connection will not
be reused if it is currently processing a chunk larger than this.

CURLMOPT_PIPELINING_SITE_BL - A blacklist of hosts that don't allow
pipelining.

CURLMOPT_PIPELINING_SERVER_BL - A blacklist of server types that don't allow
pipelining.

See the curl_multi_setopt() man page for details.

The flag can be used in pycurl-based applications where using the multi
interface would not be acceptable because of the performance lost caused
by implementing the select() loop in python.

Bug: http://curl.haxx.se/bug/view.cgi?id=1168
Downstream Bug: https://bugzilla.redhat.com/919127

No API change involved.

Info: http://curl.haxx.se/mail/lib-2013-02/0234.html

CURLOPT_USE_SSL should be set to CURLUSESSL_* and nothing else in modern
libcurl versions.

For active FTP connections, applications may need setting the sockopt after accept() call returns successful. This fix gives a call to the callback registered with CURL_SOCKOPTFUNCTION option. Also a new sock type - CURLSOCKTYPE_ACCEPT - is added. This type is to be passed to application callbacks with - purpose - parameter. Applications may use this parameter to distinguish between socket types.

CURLSSH_AUTH_AGENT is a new auth type for SSH

Make sure CURL_VERSION_SSPI is present and works as in previous releases
for ABI and API compatibility reasons.

Added Windows SSPI version information to the curl version string when
SCHANNEL SSL is not enabled, as the version of the library should also
be included when SSPI is used to generate security contexts.

Removed SSPI from the feature list as the features are GSS-Negotiate,
NTLM and SSL depending on the usage of the SSPI library.

Info: http://curl.haxx.se/mail/lib-2012-04/0170.html