Add SetPreviousMouseState and SetPreviousKeyboardState (#664)
Add SetPreviousMouseState and SetPreviousKeyboardState (#664)

Add a couple useful functions for manipulating input. For example, if you call `SetCurrentMouseState()`  then you can't control values like `Input.MousePositionDelta`, which depend on the previous input state.
ericmbernier/Nez,prime31/Nez,prime31/Nez,prime31/Nez