Appveyor images are named after the Visual Studio version they contain.
But we compile using MinGW, not Visual Studio.
We use these images because they have different Windows versions.

Closes bug 28826.

This patch explicitly specifies the path to our OpenSSL dependency and
disables the installation of an external OpenSSL version and instead
uses the OpenSSL version available from the MinGW environments.

See: https://bugs.torproject.org/28574

Always show the configure and test logs, and upload them as build
artifacts, when building for Windows using Appveyor CI.

Implements 28459.

Documentation for 28399, 28454, and previous fixes.

The mingw zstd from MSYS2 doesn't come with a pkg-config file.

Fixes 28454 on Tor 0.3.4.1-alpha.

Fixes 28399 on 0.3.4.1-alpha.

Stop installing MSYS2 packages.
We're compiling for mingw, so we only need mingw packages.

Run pacman in verbose mode.

Explicitly install pkg-config and xz, to future-proof our builds.

Diagnostics for 28399.

Build tor on Windows Server 2012 R2 and Windows Server 2016 using
Appveyor's CI.

Closes ticket 28318.

This package conflicts with a preinstalled mingw openssl.

Fixes bug 27943. I think this was an appveyor change, not a Tor bug.

Closes ticket 27765

This commit also changes the appveyor file to a unified line ending
style, since the old one was pretty confused.  Use "-b" to see the
real differences.

As of August 29, 2018, Appveyor images come with gcc 8.2.0 by
default. 64-bit Windows executables compiled with gcc 8.2.0 and
tor's --enable-gcc-hardening crash.

Fixes bug 27460; bugfix on 0.3.4.1-alpha.

Fixes bug 27464; bugfix on 0.3.4.1-alpha.

Also zip the full logs, and upload them as build artifacts.

Implements ticket 27430.

Implements 27449.

Implements 27275.

Original by Marcin Cieślak, with modifications from Isis Lovecruft
and Nick Mathewson.