Closes https://github.com/curl/curl/pull/5754

Except where the results are only used for character output.
getenv is not touched because it's part of the public API, and having
it return UTF-8 instead of ANSI would be a breaking change.

Fixes https://github.com/curl/curl/issues/5658
Fixes https://github.com/curl/curl/issues/5712
Closes https://github.com/curl/curl/pull/5718

To avoid collision risks with private libcurl symbols when linked with
static versions (or just versions not hiding internal symbols).

Reported-by: hydra3333 on github
Fixes #5219
Closes #5234

Follow-up to 1fc0617dcc

- Change tool_util.c tvnow() for Windows to match more closely to
  timeval.c Curl_now().

- Create a win32 init function for the tool, since some initialization
  is required for the tvnow() changes.

Prior to this change the monotonic time function used by curl in Windows
was determined at build-time and not runtime. That was a problem because
when curl was built targeted for compatibility with old versions of
Windows (eg _WIN32_WINNT < 0x0600) it would use GetTickCount which wraps
every 49.7 days that Windows has been running.

This change makes curl behave similar to libcurl's tvnow function, which
determines at runtime whether the OS is Vista+ and if so calls
QueryPerformanceCounter instead. (Note QueryPerformanceCounter is used
because it has higher resolution than the more obvious candidate
GetTickCount64). The changes to tvnow are basically a copy and paste but
the types in some cases are different.

Ref: https://github.com/curl/curl/issues/3309

Closes https://github.com/curl/curl/pull/4847

- Disable warning C4127 "conditional expression is constant" globally
  in curl_setup.h for when building with Microsoft's compiler.

This mainly affects building with the Visual Studio project files found
in the projects dir.

Prior to this change the cmake and winbuild build systems already
disabled 4127 globally for when building with Microsoft's compiler.
Also, 4127 was already disabled for all build systems in the limited
circumstance of the WHILE_FALSE macro which disabled the warning
specifically for while(0). This commit removes the WHILE_FALSE macro and
all other cruft in favor of disabling globally in curl_setup.

Background:

We have various macros that cause 0 or 1 to be evaluated, which would
cause warning C4127 in Visual Studio. For example this causes it:

    #define Curl_resolver_asynch() 1

Full behavior is not clearly defined and inconsistent across versions.
However it is documented that since VS 2015 Update 3 Microsoft has
addressed this somewhat but not entirely, not warning on while(true) for
example.

Prior to this change some C4127 warnings occurred when I built with
Visual Studio using the generated projects in the projects dir.

Closes https://github.com/curl/curl/pull/4658

- remove unused variables
- declare conditionally used variables conditionally
- suppress unused variable warnings in the CMake tests
- remove dead variable stores
- consistently use WIN32 macro to detect Windows

Closes https://github.com/curl/curl/pull/3739

Stick to "Schannel" everywhere. The configure option --with-winssl is
kept to allow existing builds to work but --with-schannel is added as an
alias.

Closes #3504

The partial struct initialization in 397664a065abffb7c3445ca9 caused
a warning on uninitialized MODULEENTRY32 struct members:

  /src/tool_doswin.c:681:3: warning: missing initializer for field
  'th32ModuleID' of 'MODULEENTRY32 {aka struct tagMODULEENTRY32}'
  [-Wmissing-field-initializers]

This is sort of a bogus warning as the remaining members will be set
to zero by the compiler, as all omitted members are. Nevertheless,
remove the warning by omitting all members and setting the dwSize
members explicitly.

Closes #3254
Reviewed-by: Marcel Raad <Marcel.Raad@teamviewer.com>
Reviewed-by: Jay Satiro <raysatiro@yahoo.com>

- Add an undocumented diagnostic option for Windows to show the full
  paths of all loaded modules regardless of whether or not libcurl
  initialization succeeds.

This is needed so that in the CI we can get a list of all DLL
dependencies after initialization (when they're most likely to have
finished loading) and then package them as artifacts so that a
functioning build can be downloaded. Also I imagine it may have some use
as a diagnostic for help requests.

Ref: https://github.com/curl/curl/pull/3103

Closes https://github.com/curl/curl/pull/3208