Float Negation -.x

[Mehgugs]

Currently we don't have a "dot operator" for negating a float. This means to negate a float we have to use 0.0 -. x or a similar expression.

This confused me when doing some float math for a second, and I also think it would make code a little bit more readable.

I'm happy to have a go at a PR for this by following how the int negation is implemented as a guide.