Use LongToHandle to convert from long to HANDLE in the Win32
implementation.
This should fix the following warning when compiling with
MSVC 11 (2012) in 64-bit mode:
lib\curl_threads.c(113): warning C4306:
'type cast' : conversion from 'long' to 'HANDLE' of greater size

Closes https://github.com/curl/curl/pull/1717

Reported-by: Max Dymond

There are some bugs in how timers are managed for a single easy handle
that causes the wrong "next timeout" value to be reported to the
application when a new minimum needs to be recomputed and that new
minimum should be an existing timer that isn't currently set for the
easy handle.  When the application drives a set of easy handles via the
`curl_multi_socket_action()` API (for example), it gets told to wait the
wrong amount of time before the next call, which causes requests to
linger for a long time (or, it is my guess, possibly forever).

Bug: https://curl.haxx.se/mail/lib-2017-07/0033.html

.. to catch accidental use of deprecated error codes.

Ref: https://github.com/curl/curl/issues/1688#issuecomment-316764237

Fixes #1669
Closes #1713

test 1429 and 1433 were updated to work with the stricter HTTP status line
parser.

Closes #1714
Reported-by: Brian Carpenter

Fixes https://github.com/curl/curl/issues/1688
Closes https://github.com/curl/curl/pull/1712

Follow-up to 171f8ded and de6de94c.

Bug: https://github.com/curl/curl/commit/de6de94#commitcomment-23370851
Reported-by: Daniel Stenberg

Closes #1674

It was misspelled as CURL_ERROR in commit
2d86e8d1.

Closes https://github.com/curl/curl/pull/1686

Follow-up to 171f8ded.

Ref: https://github.com/curl/curl/issues/1704

Follow-up to 4dee50b9.

Ref: https://github.com/curl/curl/pull/1693

Reported-by: olesteban at github
Fixes #1704

The headers of librtmp declare the socket as `int`, and on Windows, that
disagrees with curl_socket_t.

Bug: #1652

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

... to make all libcurl internals able to use the same data types for
the struct members. The timeval struct differs subtly on several
platforms so it makes it cumbersome to use everywhere.

Ref: #1652
Closes #1693

... which made --tlsv1.2 not work because it would blank the max tls
version variable.

Reported-by: Nick Miyake
Bug: #1703

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

Closes #1675
Closes #1683

... to silence warning.

... causing a SIGSEGV in showit() in case the handle used to initiate
the connection has already been freed.

This commit fixes a bug introduced in curl-7_19_5-204-g5f0cae80.

Reported-by: Rob Sanders
Bug: https://bugzilla.redhat.com/1436158

No changes in behavior intended by this commit.

MSVC warns that gethostbyname is deprecated. Always use getaddrinfo
instead to fix this when IPv6 is enabled, also for IPv4 resolves. This
is also consistent with what libcurl does.

Closes https://github.com/curl/curl/pull/1682

- s/SessionHandle/Curl_easy/

Bug: https://github.com/curl/curl/commit/eb16305#commitcomment-23035670
Reported-by: Gisle Vanem

Older GCC warns:
/tests/server/rtspd.c:1194:10: warning: missing braces around
initializer [-Wmissing-braces]

Fix this by using memset instead of an initializer.

With warning level 4, MSVC warns about assignments within conditional
expressions. Change the while loop to a do-while loop to fix this. This
change is also consistent with CODE_STYLE.md.

MSVC warns when implicitly casting -1 to unsigned long.

warning C4701: potentially uninitialized local variable 'req' used

Disabled in cda19a34. It only needs to
be disabled for libcurl.

This is consistent with 7bc64561, which
changed the warning level from 3 to 4 for the Visual Studio project
files. But disable the level 4 warning C4127 "conditional expression is
constant", as that one is issued by older versions of the Windows SDK
as well as curl itself under some circumstances.

Closes https://github.com/curl/curl/pull/1667

Install libidn2 to increase test coverage (IDN tests)

Closes https://github.com/curl/curl/pull/1673

... to get warnings also on Linux/GCC and OSX/clang.

Closes https://github.com/curl/curl/pull/1666

Install libssh2 to increase test coverage (SFTP, SCP)

... to avoid compiler warnings if the user doesn't want
WIN32_LEAN_AND_MEAN.

It's defined for all build systems in curl_setup.h since commit
beb08481. This caused macro
redefinition warnings in the configure builds.

Closes https://github.com/curl/curl/pull/1677

Make sure to always define WIN32_LEAN_AND_MEAN before including any
Windows headers to avoid pulling in unnecessary headers. This avoids
unnecessary macro clashes and compiler warnings.

Ref: https://github.com/curl/curl/issues/1562
Closes https://github.com/curl/curl/pull/1672

This is a follow-up to af021625 which removed (SET_)ERRNO macros. That
commit was an earlier draft that I committed by mistake, which was then
remedied by a5834e52 and e909de65, and now this commit. With this commit
there is now no difference between the current code and the changes that
were approved in the final draft.

Thanks-to: Max Dymond, Marcel Raad, Daniel Stenberg, Gisle Vanem
Ref: https://github.com/curl/curl/pull/1589

Closes https://github.com/curl/curl/pull/1671