Move curl_mime_initpart() and curl_mime_cleanpart() calls to lower-level
functions dealing with UserDefined structure contents.
This avoids memory leakages on curl-generated part mime headers.
New test 2073 checks this using the cli tool --next option: it
triggers a valgrind error if bug is present.

Bug: https://curl.haxx.se/mail/lib-2017-12/0060.html
Reported-by: Martin Galvan

- When zlib version is < 1.2.0.4, process gzip trailer before considering
extra data as an error.
- Inflate with Z_BLOCK instead of Z_SYNC_FLUSH to maximize correct data
and minimize corrupt data output.
- Do not try to restart deflate decompression in raw mode if output has
started or if the leading data is not available anymore.
- New test 232 checks inflating raw-deflated content.

Closes #2068

Some error codes were not yet defined in brotli 0.6.0: do not issue code
for them in this case.

Bug: #2175

[ci skip]

scan-build would warn on a potential access of an uninitialized
buffer. I deem it a false positive and had to add this somewhat ugly
work-around to silence it.

A scan-build warning.

This broke in 07cb27c9. Make sure to return 'result' properly. Pointed
out by scan-build!

Bug: #2174

Follow-up to c92d2e14

Closes #2172

... to make it clearer that the options want address-only, while the
headers in an email can also have the real name.

Assisted-by: Sean MacLennan

... as I reran the contrithanks script after the mailmap name fixups.

... for the CURLOPT_TIMEOUT, CURLOPT_CONNECTTIMEOUT and
CURLOPT_SERVER_RESPONSE_TIMEOUT range checks.

Reported-by: Dominik Hölzl
Bug: https://curl.haxx.se/mail/lib-2017-12/0037.html

Closes #2173

Fixed undefined symbol of getenv() which does not exist when compiling
for Windows 10 App (CURL_WINDOWS_APP). Replaced getenv() with
curl_getenv() which is aware of getenv() absence when CURL_WINDOWS_APP
is defined.

Closes #2171

Suggested-by: Rainer Canavan

Closes #2126

This reverts commit 9ffad8eb.

It was actually added rather recently in 8e8afa82 due to a crash
that would otherwise happen in the RTSP code. As I don't think we've
fixed that behavior yet, we better keep this work-around until we have
fixed it better.

Prune the DNS cache immediately after the dns entry is unlocked in
multi_done. Timed out entries will then get discarded in a more orderly
fashion.

Test506 is updated

Reported-by: Oleg Pudeyev

Fixes #2169
Closes #2170

Prior to this change SSLKEYLOGFILE used line buffering on WIN32 just
like it does for other platforms. However, the Windows CRT does not
actually support line buffering (_IOLBF) and will use full buffering
(_IOFBF) instead. We can't use full buffering because multiple processes
may be writing to the file and that could lead to corruption, and since
full buffering is the only buffering available this commit disables
buffering for Windows SSLKEYLOGFILE entirely (_IONBF).

Ref: https://github.com/curl/curl/pull/1346#issuecomment-350530901

... to help users understand what is or isn't done!

Closes #1900

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

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

These are OS/2-specific things added to the code in the year 2000. They
were always ugly. If there's any user left, they still don't need it
done this way.

Closes #2166

- Allow proxy_ssl to be checked for pending data even when connssl does
  not yet have an SSL handle.

This change is for posterity. Currently there doesn't seem to be a code
path that will cause a pending data check when proxyssl could have
pending data and the connssl handle doesn't yet exist [1].

[1]: Recall that an https proxy connection starts out in connssl but if
the destination is also https then the proxy SSL backend data is moved
from connssl to proxyssl, which means connssl handle is temporarily
empty until an SSL handle for the destination can be created.

Ref: https://github.com/curl/curl/commit/f4a6238#commitcomment-24396542

Closes https://github.com/curl/curl/pull/1916

That data is only ever used by the CURLOPT_INTERLEAVEFUNCTION callback
and that option isn't set or used by the curl tool!

Updates the 9 tests that verify --libcurl

Closes #2167

... error messages are _not_ sent to stderr if this is not set.

Fixes #2076
Closes #2125

Make it use a max 10Hz update frequency for this case as well. Return
early if the "point" hasn't moved since last invoke.

Reported-by: Elliot Saba

Fixes #2158
Closes #2163

...the former link is dead.

Reported-by: Frank Gevaerts

Fixes #2088
Closes #2157

... to allow build on older Linux dists (specifically CentOS 4.8 on gcc
4.8.5)

Closes #2160

... to aid debugging openldap library using its built-in debug messages.

Closes #2159