Tracing np.add, all the way down

The `.c.src` files with the @arch@ like dispatching logic is specific to numpy. Also, they are currently making efforst to shift to C++ templates using Google's Highway project. I worked on porting `np.negative` to it!

I sort of wish they used c++ for some of the template stuff, especially since the code base already seems to have some C++ iirc. I also contributed a tiny bit in the past, and their C template system was a surprise. (but this is cool and I love numpy anyway lol)

That was some lovely spelunking XD