Build fix for the latest LLVMContext changes (LLVM r75445) This shouldn't break the build with older LLVM revs. We include LLVMContext.h in gen/llvm.h now to make the transition a little bit easier.

struct Vector {
        union { float x; float y; }
        const static Vector zero = { x : 0, y : 0 };
}

struct HBoxLayout {
        Vector padding  = Vector.zero;
}