... and make sure to avoid integer overflows with really large values.

Reported-by: 刘佩东
Fixes #2371
Closes #2373

follow-up to e04417d9

Reported-by: Michael Kaufmann
Fixes #2357
Closes #2362

... as it is interesting for many users.

Closes #2349

Check for existence of import and static libraries with documented names
and use them if they do. Fallback to previous names.

According to
https://github.com/madler/zlib/blob/master/win32/README-WIN32.txt on
Windows, the names of the import library is "zdll.lib" and static
library is "zlib.lib".

closes #2354

gss_seal/gss_unseal have been deprecated in favor of
gss_wrap/gss_unwrap with GSS-API v2 from January 1997 [1]. The first
version of "The Kerberos Version 5 GSS-API Mechanism" [2] from June
1996 already says "GSS_Wrap() (formerly GSS_Seal())" and
"GSS_Unwrap() (formerly GSS_Unseal())".

Use the nondeprecated functions to avoid deprecation warnings.

[1] https://tools.ietf.org/html/rfc2078
[2] https://tools.ietf.org/html/rfc1964

Closes https://github.com/curl/curl/pull/2356

Added test 1265 that verifies.

Reported-by: steelman on github
Fixes #2353
Closes #2355

... so that the CI and more detects compiler warnings/errors properly!

Closes #2337

On MinGW and Cygwin, GCC and clang have been complaining about macro
redefinitions since 4272a0b0. Fix this
by undefining the macros before redefining them as suggested in
https://github.com/curl/curl/pull/2269.

Suggested-by: Daniel Stenberg

When targeting x64, MinGW-w64 complains about conversions between
32-bit long and 64-bit pointers. Fix this by reusing the
GNUTLS_POINTER_TO_SOCKET_CAST / GNUTLS_SOCKET_TO_POINTER_CAST logic
from gtls.c, moving it to warnless.h as CURLX_POINTER_TO_INTEGER_CAST /
CURLX_INTEGER_TO_POINTER_CAST.

Closes https://github.com/curl/curl/pull/2341

Update clang to version 3.9 and GCC to version 6.

Closes https://github.com/curl/curl/pull/2345

Fixes #2342

- Add OpenSSL 1.1.1 to the header/library version lists.

- Detect OpenSSL 1.1.1 library using its function ERR_clear_last_mark,
  which was added in that version.

Prior to this change an erroneous header/library mismatch was caused by
lack of OpenSSL 1.1.1 detection. I tested using openssl-1.1.1-pre1.

Closes https://github.com/curl/curl/pull/2335

Detected using the `codespell` tool.

Also contains one URL protocol upgrade.

Closes https://github.com/curl/curl/pull/2334

Reported-by: Stefan Kanthak and Rod Widdowson

Fixes #2325

- Add macros to the top of the makefile for rc and mt utilities so that
  it is easier to change their locations.

Bug: https://curl.haxx.se/mail/lib-2018-02/0075.html
Reported-by: Stefan Kanthak

Closes https://github.com/curl/curl/issues/2329

Co-authored-by: Stefan Kanthak

Closes https://github.com/curl/curl/issues/2330
Closes https://github.com/curl/curl/pull/2331

- Add new option CURLOPT_RESOLVER_START_FUNCTION to set a callback that
  will be called every time before a new resolve request is started
  (ie before a host is resolved) with a pointer to backend-specific
  resolver data. Currently this is only useful for ares.

- Add new option CURLOPT_RESOLVER_START_DATA to set a user pointer to
  pass to the resolver start callback.

Closes https://github.com/curl/curl/pull/2311

- In keeping with the naming of our other connect timeout options rename
  CURLOPT_HAPPY_EYEBALLS_TIMEOUT to CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS.

This change adds the _MS suffix since the option expects milliseconds.
This is more intuitive for our users since other connect timeout options
that expect milliseconds use _MS such as CURLOPT_TIMEOUT_MS,
CURLOPT_CONNECTTIMEOUT_MS, CURLOPT_ACCEPTTIMEOUT_MS.

The tool option already uses an -ms suffix, --happy-eyeballs-timeout-ms.

Follow-up to 2427d94c which added the lib and tool option yesterday.

Ref: https://github.com/curl/curl/pull/2260

SASL PLAIN is a standard, LOGIN only a draft. The LOGIN draft says
PLAIN should be used instead if available.

- Add new option CURLOPT_HAPPY_EYEBALLS_TIMEOUT to set libcurl's happy
  eyeball timeout value.

- Add new optval macro CURL_HET_DEFAULT to represent the default happy
  eyeballs timeout value (currently 200 ms).

- Add new tool option --happy-eyeballs-timeout-ms to expose
  CURLOPT_HAPPY_EYEBALLS_TIMEOUT. The -ms suffix is used because the
  other -timeout options in the tool expect seconds not milliseconds.

Closes https://github.com/curl/curl/pull/2260

Follow-up to 50d1b337.

Caught by AppVeyor.