Method setData

API/fleece/Mutable.hh:34–34

        void operator= (const char *v)              {FLSlot_SetString(_slot, slice(v));}
        void operator= (const std::string &v)       {FLSlot_SetString(_slot, slice(v));}
        void setData(slice v)                       {FLSlot_SetData(_slot, v);}
        void operator= (Value v)                    {FLSlot_SetValue(_slot, v);}
        void operator= (std::nullptr_t)             {FLSlot_SetValue(_slot, nullptr);}