.. and preprocessor check TLS session info is defined for all backends.

Some systems have special files that report as 0 bytes big, but still
contain data that can be read (for example /proc/cpuinfo on
Linux). Starting now, a zero byte size is considered "unknown" size and
will be read as far as possible anyway.

Reported-by: Jesse Tan

Closes #681

- Warn if --with-ca-bundle file does not exist.

- Warn if --with-ca-path directory does not contain certificates.

- Improve help messages for both.

Example configure output:

  ca cert bundle:   /some/file   (warning: certs not found)
  ca cert path:     /some/dir   (warning: certs not found)

Bug: https://github.com/curl/curl/issues/404
Reported-by: Jeffrey Walton

... as when pipelining is used, we read things into a unified buffer and
we don't do that with HTTP/2. This could then easily make programs that
set CURLMOPT_PIPELINING = CURLPIPE_HTTP1|CURLPIPE_MULTIPLEX to get data
intermixed or plain broken between HTTP/2 streams.

Reported-by: Anders Bakken

The two options are almost the same, except in the case of OpenSSL:

CURLINFO_TLS_SESSION OpenSSL session internals is SSL_CTX *.

CURLINFO_TLS_SSL_PTR OpenSSL session internals is SSL *.

For backwards compatibility we couldn't modify CURLINFO_TLS_SESSION to
return an SSL pointer for OpenSSL.

Also, add support for the 'internals' member to point to SSL object for
the other backends axTLS, PolarSSL, Secure Channel, Secure Transport and
wolfSSL.

Bug: https://github.com/curl/curl/issues/234


Reported-by:  <dkjjr89@users.noreply.github.com>

Bug: https://curl.haxx.se/mail/lib-2015-09/0127.html
Reported-by: Michael König

The internal Curl_done() function uses Curl_expire() at times and that
uses the timeout list. Better clean up the list once we're done using
it. This caused a segfault.

Reported-by: 蔡文凱
Bug: https://curl.haxx.se/mail/lib-2016-02/0097.html

DSA is no longer supported by OpenSSH 7.0, which causes all SCP/SFTP
test cases to be skipped.  Using RSA for host authentication works with
both old and new versions of OpenSSH.

Reported-by: Karlson2k

Closes #676

- Add tests.

- Add an example to CURLOPT_TFTP_NO_OPTIONS.3.

- Add --tftp-no-options to expose CURLOPT_TFTP_NO_OPTIONS.

Bug: https://github.com/curl/curl/issues/481

Some TFTP server implementations ignore the "TFTP Option extension"
(RFC 1782-1784, 2347-2349), or implement it in a flawed way, causing
problems with libcurl. Another switch for curl_easy_setopt
"CURLOPT_TFTP_NO_OPTIONS" is introduced which prevents libcurl from
sending TFTP option requests to a server, avoiding many problems caused
by faulty implementations.

Bug: https://github.com/curl/curl/issues/481

Closes #672

Sync with lib/Makefile.m32 which already uses those variables.

Bug: https://github.com/curl/curl/pull/670

If any parameter in a HTTP DIGEST challenge message is present multiple
times, memory allocated for all but the last entry should be freed.

Bug: https://github.com/curl/curl/pull/667

Reported-by:  <neex@users.noreply.github.com>

Bug: https://github.com/curl/curl/issues/666


Reported-by:  <baumanj@users.noreply.github.com>

Bug: https://github.com/curl/curl/issues/666


Reported-by:  <baumanj@users.noreply.github.com>

First version, try this out!

To hide github specific files somewhat from the rest.

Reported-By: Gisle Vanem

At one point during the development of HTTP/2, the commit 133cdd29
introduced automatic decompression of Content-Encoding as that was what
the spec said then. Now however, HTTP/2 should work the same way as
HTTP/1 in this regard.

Reported-by: Kazuho Oku

Closes #661

nghttp2 callback deals with TLS layer and therefore the header does not
need to be broken into chunks.

Bug: https://github.com/curl/curl/issues/659
Reported-by: Kazuho Oku

by using API instead of accessing an internal structure.
This is required starting OpenSSL 1.1.0-pre3.

Closes #650

Change the example in the docs for CURLOPT_CONNECTTIMEOUT_MS to use
CURLOPT_CONNECTTIMEOUT_MS instead of CURLOPT_CONNECTTIMEOUT.

Closes #653

libssh2_scp_recv2 is introduced in libssh2 1.7.0 - to be released "any
day now.

Closes #451

Bug: https://github.com/curl/curl/pull/651