Like we do for the TravisCI YAML file, use the leading dot notation to
hide the Appveyor YAML file from directory listing on Unix-like OSes.

This way, we don't have to depend on Python2 on newer OSes.

Instead of having Meson determine the invocator through the shebang
line we explicitly pass the script file to the Python interpreter.

This will allow us to either use Python3 or Python2, or whatever
Python.exe is available on Windows.

GLEW has grown support for OpenGL 3.2+ core contexts over the years.
Everything else has stayed pretty much the same, though, so you should
still use Epoxy over libGLEW.

Gamifying the development experience, once achievement at a time.

As libtool suggest we do; this also allows using ACLOCAL_AMFLAGS inside
build that create a separate environment with their own m4 macros, like
jhbuild and Cerberus.

In order to avoid a warning from autoreconf, we create the empty macros
directory during the autogen.sh step; aclocal would create the directory
for us anyway, but different versions of autotools may have different
behaviours.

Closes: #58

Closes #95

Appveyor is a CI infrastructure like Travis, but oriented at building on
Windows environment, as opposed to Linux and macOS.

By using Appveyor we can test changes to Epoxy and make sure that
Windows builds won't break.

Additionally, Appveyor allows to deploy build artefacts, which means we
can generate builds for Epoxy releases.

Signed-off-by: Emmanuele Bassi <ebassi@gnome.org>

We don't need to list the source files as we use a glob rule in the
Doxyfile itself.

We don't need to list the source files as we use a glob rule in the
Doxyfile itself.