No working appveyor config #19
Description
I have made a working Travis config. I would like a working appveyor config now. It seems AppVeyor offer MinGW and various Visual Studio installations in their standard build. I would like as many of the modern-ish Windows possibilities being tested.
Unfortunately getting MSVC into the path for command-line stuff has defeated me. The closest I have got is using vcvarsall.bat (from https://stackoverflow.com/questions/42855857/how-to-find-ms-c-c-compilers-in-appveyor), but it is saying it can't find the 'include' dirs, and indeed the winnt\microsft\vpp40\mk.cmd failed because it couldn't find headers.