I don't know the details, grubba is the one that has been trying to get 8.1 to build on the existing VC9 Windows build machines. So anything that doesn't break VC9 is probably fine.
I'm dedicating all my Windows development time* to get VC14 up and running. If that gets done we can probably go all out C99. * Windows is boring. It gets maybe 45min per week. There is very slow progress, but progress no the less.
