Changes the GS::VertexBuffer storage to be one continuous buffer that is properly aligned and is also now used for GS::Vertex. This halves the necessary memory, removes reallocation cost and removes the copy necessary to get things onto the GPU.
Related: #9
The previous fix unfortunately didn't actually fix it and instead made the crash invisible at first and then corrupt the heap at a later point. With this, VS2013 and VS2015 create code identical to what VS2017 creates, and no longer seem to crash.
Related: #9