Suggested-by: Rainer Canavan

Closes #2126

- Change "never does nothing" double-negative to "never does anything".

Closes https://github.com/curl/curl/pull/2168

...the former link is dead.

Reported-by: Frank Gevaerts

... due it relying on pthreads to link.

Lists all SSL backends that were enabled at build-time.

Suggested-by: Oleg Pudeyev
Fixes #2128

Connections that are used for HTTP/1.1 Pipelining or HTTP/2 multiplexing
only get additional transfers added to them if the existing connection
is held by the same multi or easy handle. libcurl does not support doing
HTTP/2 streams in different threads using a shared connection.

Closes #2152

Closes #2145

Signed-off-by: Nikos Mavrogiannopoulos <nmav@gnutls.org>

Reported-by: Dima Tisnek

This bit is no longer used. It is not clear what it meant for users to
"init the TLS" in a world with different TLS backends and since the
introduction of multissl, libcurl didn't properly work if inited without
this bit set.

Not a single user responded to the call for users of it:
https://curl.haxx.se/mail/lib-2017-11/0072.html

Reported-by: Evgeny Grin
Assisted-by: Jay Satiro

Fixes #2089
Fixes #2083
Closes #2107

Fixes #2097
Closes #2108

Fixes #2106
Reported-by: youngchopin on github

- Add braces around multi-line if statement.

Closes https://github.com/curl/curl/pull/2096

... so that IPv6 addresses can be passed like they can for connect-to
and how they're used in URLs.

Added test 1324 to verify
Reported-by: Alex Malinovich

Fixes #2087
Closes #2091

Closes #1455

The --interface command (CURLOPT_INTERFACE option) already uses
SO_BINDTODEVICE on Linux, but it tries to parse it as an interface or IP
address first, which fails in case the user passes a VRF.

Try to use the socket option immediately and parse it as a fallback
instead.  Update the documentation to mention this feature, and that it
requires the binary to be ran by root or with CAP_NET_RAW capabilities
for this to work.

Closes #2024

Closes #2043

... even when there's no socket to wait for, the timeout can still be
very short.

This uses the brotli external library (https://github.com/google/brotli).
Brotli becomes a feature: additional curl_version_info() bit and
structure fields are provided for it and CURLVERSION_NOW bumped.

Tests 314 and 315 check Brotli content unencoding with correct and
erroneous data.

Some tests are updated to accomodate with the now configuration dependent
parameters of the Accept-Encoding header.

This is implemented as an output streaming stack of unencoders, the last
calling the client write procedure.

New test 230 checks this feature.

Bug: https://github.com/curl/curl/pull/2002
Reported-By: Daniel Bankhead

Also upgrade test 1133 to cover this case and clarify man page about
form data quoting.

Bug: https://github.com/curl/curl/issues/2022
Reported-By: omau on github

Updated docs to include support for RFC7616

Signed-off-by: Florin <petriuc.florin@gmail.com>

Closes #1934

Closes #2002

Removed done stuff. Removed entries no longer considered for the near
term.

Closes #2028

"PR-welcome" was the former name.