Changed appveyor config to use MSYS2 + MinGW-w64 instead of MinGW/MSYS
Changed appveyor config to use MSYS2 + MinGW-w64 instead of MinGW/MSYS

offa/Criterion,kaidowei/Criterion,Snaipe/Criterion,offa/Criterion,kaidowei/Criterion,offa/Criterion,am11/Criterion,offa/Criterion,Snaipe/Criterion,Snaipe/Criterion,am11/Criterion,kaidowei/Criterion,a1lu/Criterion,kaidowei/Criterion,am11/Criterion,a1lu/Criterion,am11/Criterion,am11/Criterion,Snaipe/Criterion,Snaipe/Criterion,kaidowei/Criterion,a1lu/Criterion,offa/Criterion,a1lu/Criterion,a1lu/Criterion