The tests have never run successfully and we do have successful builds of mingw-w64, so remove these CI builds which do not add value.
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
