MSVC build of Piglit was broken for over a month.  No point in
sustaining it.

Building with MinGW is the way forward.
Reviewed-by: Brian Paul <brianp@vmware.com>

Disabled by default, as I'm not sure it's worth supporting MSVC build.
Acked-by: Dylan Baker <dylan@pnwbakers.com>

This replaces the previous appveyor.yml with python tox tests.

See https://ci.appveyor.com/project/jrfonseca/piglit-fc01r for the runs.
Acked-by: Dylan Baker <dylan@pnwbakers.com>

Also enables the target in travis and appveyor.
Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>

This currently doesn't test building piglit (the C/C++ code), only the
python bits, and only the framework, not the generators. It's probably
worth adding support for all of that, but it's a more involved project,
and I'm just trying to not break the framework on windows anymore.
Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>