reimplement room_to_displaay_x / y

[jack27121]

it's in the stanncam code it's just uncommented

this might work, but haven't tested it

    /// @function room_to_display_x
    /// @description returns the room x position as the position on the display relative to camera
    /// @param {Real} x_
    /// @returns {Real}
    /// @ignore
    static room_to_display_x = function(x_){
        return ((x_-get_y()-x_frac) / get_zoom_x()) * stanncam_get_res_scale_x();
    }

[bfrymire]

Duplicate of #51