These tests were not being taken into consideration for the failure of
the test. They've been failing for a while now, but we hadn't noticed as
Travis was reporting the builds successful.

This reverts commit ba6c53b91b1d9c9dc49b7c0d8e8efbd9842c31dc.

cache mingw-w64 downloads

quiet curl and 7zip

run appveyor steps in cmd for mingw

use MSYS makefiles generator

add bash script for running mingw on appveyor

add --login and fix run paths

use msys style path to appveyor-mingw.sh

add mingw path to /etc/fstab

Run shell scripts through shellcheck

The sshd on OSX has stopped responding to the setting which this test
assumes is there, so let's disable it until we can figure out what's
happening.